Human Evolution on Trial - Into Australia - by Terry Toohill

Human Evolution on Trial - Into Australia

The Australian Aborigines’ long isolation at a remote point of the human star provides useful evidence supporting the wave theory of Human Evolution. Their isolation from developments in other parts of the world meant they preserved elements of a very ancient stone technology when Europeans first reached there. This primitive technology in no way indicates they were, or are, any less intelligent or able than any others of us are. They are quite capable of becoming lawyers, economists or accountants. Both the technology and the culture people possess are simply accidents of history. Many technological and cultural innovations in other parts of the world simply failed to reach that continent although there is evidence some technologies originally taken into Australia were actually lost there. The jury will continue to see many more examples of change failing to reach marginal areas.


The map of the world based on the first principal component of genetic variation (therefore accounting for the greatest proportion of genetic variation among all humans) shows one extreme is widespread. It includes all of Africa and most of Europe, Arabia and Turkey. The opposite extreme is confined to the pre-European Australians (Cavalli-Sforza et al 1994). This presumably indicates many genetic changes in the rest of the world also failed to reach Australia. Interestingly the map shows Asians and American Indians could be a sort of hybrid between Australian Aborigines and the western people (map 16).

The Dreamtime

As far as I’m aware there is no certain evidence humans were in Australia as long ago as 50,000 years but dates of 30,000 to 40,000 are generally accepted. Although there is no direct evidence humans were involved in the extinction of the large animals in Australia the timing of “Extinctions” [What Have We Done?] indicates humans were present by at least 50,000 years ago. Where the archeological evidence and the extinction evidence don’t quite agree go with the extinctions. The earliest human remains found in Australia are of what has been described as “anatomically modern man” although in many ways it could be called “ultra-modern”. This population is known as Mungo Man as the remains were found near what is today a dried up Lake Mungo. Remains of similar-looking people have been found at other sites in Australia. Alan Thorne claims to have dated one Mungo Man skeleton (although many people believe it is actually a woman) at 60,000 years (Adcock et al 2001). This date is irrelevant for the main claims about the particular skeleton (“MtEve” [Mungo Man]) and there is no obvious reason why the skeleton’s date must be wrong although it is disputed. The particular Mungo Man didn’t belong to the mtEve line, although closer to that line than to Neanderthal lines. It parted from the mtEve line about 250,000 years ago.

There has been debate about the actual pattern of migration both into and within Australia. Most people interpret the evidence within Australia as showing an expansion round the coast and up the rivers. You will soon see humans had to cross open water to even get there and so this makes sense. The argument then becomes how quickly did humans move into the continent’s interior? D. R. Woodward has suggested, quite reasonably I think, that the early immigrants were confined to watered areas (quoted in Mellars 1990). The reasoning is that they lacked containers for carrying water. Australia actually became much wetter 50,000 years ago than it is today and so access to the large grazing animals of the interior could have happened by then. The animals rapidly became extinct.

All modern Australian Aborigine mitochondrial DNA lines descend from mtEve. But whether modern humans or Homo sapiens reached Southeast Asia (and then Australia) via either India (a sub-point of the human star) or via China is not known, certainly not by me.

One theory offered is that modern humans with a coastal economy they had developed in Africa expanded through Arabia and then into Southeast Asia either along the coast of India or via the Indus and Ganges Rivers (Olson 2002). But the defence mentioned several times in Part IV that most elements of the ancient Acheulean and Levallois techniques didn’t make it to Southeast Asia. This shows there has always been a great deal of separation between east and west, the Movius line mentioned in “Technology” [Lower Paleolithic]. But Y-chromosome line K almost certainly, and mtDNA line M possibly, arrived in Southeast Asia through India (see “MtEve” [Interpretation]). You will see that they are probably part of a later movement into Australia though. Apart from this there is really no evidence for the theory although again it could be argued absence of evidence is not evidence of absence, the theory of negativity. There are actually many difficulties with the theory though. The coast is a narrow ecological zone and any rapidly moving group of human migrants would probably suffer inbreeding depression within the required number of generations. And, of course, if they had actually already invented primitive boats they could have expanded through any well-watered regions.

If we accept the idea migration routes tend to be used many times we could assume modern humans are more likely to have moved through Central Asia, the middle of the human star, and then to Southeast Asia. If they carried a water-centred culture they may have followed rivers, marshes and lakes during wetter climate conditions.

And of course the coastal culture found in Africa may be the result of an expansion of technology back from Southeast Asia or New Guinea (“Out of Africa” [Asia]). It would make sense that open water travel evolved in a region where any people who possessed it had a selective advantage. It would be easier to develop the technology with practice over short distances. A region with many small, closely packed islands would be perfect.

Wallace’s Line

At times of low sea level much of Southeast Asia becomes one continuous continent or at least a series of more, larger and closer islands. It doesn’t take much of a fall in sea level to connect Australia to New Guinea across the Arafura Sea either. But there is a gap between Australia / New Guinea and Southeast Asia that has always been open water. It is called Wallace’s Line, named after the wildlife collector Alfred Wallace. His correspondence from the region pushed Charles Darwin into publishing his great book “On the Origin of Species by Means of Natural Selection”. Wallace noticed creatures to the east and west of the line are very different. In fact most land creatures have been unable to cross Wallace’s line. It even separates the marsupials from the placental mammals.

Whichever route they took to Southeast Asia the earliest ancestors of the Australian Aborigines, Papuans and Melanesians must next have somehow crossed Wallace’s Line. Presumably they crossed some time between the onset of low sea level starting about 75,000 years ago and the presumed slight rise of sea level about 50,000 years ago (“Neanderthals et al” [Climate]). The first Australians must therefore have arrived on some sort of boat but certainly not on a luxury yacht. Bundles of reeds, bark or bamboo tied together, or simply logs, would be sufficient. A drier climate following the big freeze about 75,000 years ago may have provided more open conditions on land as well.

It is not known whether the first arrivals in Australia and New Guinea crossed Wallace’s line via Southern Indonesia (southerly route) or through Palawan and the Philippines (northerly route). But the evidence indicates that the first Australians were similar to the populations in China, Borneo and the Philippines at the time (Alan Thorne quoted in Stringer and Mckie 1996). They certainly don’t exhibit any characteristics of the most common Southeast Asian type of that time who appear to retain older Homo erectus features. These are the “Solo Man” from Java who the jury met in “Species or Not” [Expansion]. Therefore the first people Into Australia probably came by the northerly route. They would have used much the same migration route as did the much more recent Austronesian-speaking people or ancestral Polynesians (map 6). But the movement under discussion here was at a time of much lower sea level.

Whichever way they came the distance across water was less but still substantial. Japan, Taiwan and possibly some of the Ryukyu Islands were almost certainly then connected to the mainland and the shoreline of the expanded islands of the Philippines and Indonesia were closer to the mainland coast than they are today. Early versions of a common Australian Y-chromosome, C, are found throughout the region (“MtEve” [The Trees]).

Kow Swamp

In Australia fossils of a different population to Mungo Man have been found at Cohuna, Talgai and Kow Swamp. They have been dated much more recently than Mungo Man to around 15,000 to 20,000 years ago and do exhibit some characteristics found in late Homo erectus populations in Java (Jennings 1979). Even Chris Stringer and Robin McKie (1996) concede one Kow Swamp fossil “does have a skull form reminiscent of some Javanese fossils”. Some Kow Swamp characteristics are also present in some modern Australian Aborigines (Milford Wolpoff and Alan Thorne quoted in Curtis, Swisher and Lewin 2001). Many people claim that modern Australian Aborigines are a hybrid of the Mungo Man and Kow Swamp populations with neither extreme now present in the stabilised hybrid (Flood 1988). Others have suggested the two extremes actually developed within Australia (Stringer and Gamble 1993) but it is difficult to conceive of any mechanism for an original diversification and subsequent recombining in such a relatively small continent. It is much more likely to result from two separate migrations.

It is also difficult to explain the similarities between the Kow Swamp people and Asian Homo erectus by parallel evolution. Single origin supporters have argued the Australian Kow Swamp people look as much like early Africans as they do Solo Man from Southeast Asia (Stringer and McKie 1996). This is precisely what we would expect in a stabilised hybrid population. It also introduces the problem of why was the earlier Mungo population so different? Mitochondrial DNA evidence from the Kow Swamp fossils shows that they did belong to the mtEve line but the wave theory of evolution tells us their physical appearance could have been due to the survival of older nuclear DNA (and see Adcock et al 2001).

That fossil and mtDNA evidence implies a mix of Homo erectus and Homo sapiens features in the human star’s Australian point suggests very strongly that these species too could form hybrids. They had only been separated for up to one and a half million years. Actually that is probably long enough in some cases to form separate species but genes of Homo heidelbergensis had presumably earlier flowed south from the East Asian point into Southeast Asia, the ancient Australian point. It is also probable that once again combined technologies had led to a population explosion and the boundaries became porous (“Species or Not” [Both of Them]). Ground-edged stone tools were introduced to Northern Australia about the time of the Kow Swamp fossils. If these people were responsible for this introduction it would destroy the idea that Homo erectus had only primitive technology and was stupid and Homo sapiens possessed advanced technology and were cleverer.

This Kow Swamp or Solo Man population’s arrival in Australia can be explained by their acquiring elements of the boating technology off the people who had come from further north in Asia. They improved the technology and then in turn moved across Wallace’s line. They also probably moved the other way. By 10,000 years ago the hybrid people in Southeast Asia had developed into the people we met in “Pacific Population” [Hoabinhian]. You saw there that map 5 provides evidence for an expansion at some time from Southeast Asia. The Y-chromosome and mtDNA evidence suggests the same thing (“MtEve” [Interpretation]). This would have given rise to similar looking people right from India to the Northern Solomon Islands and Australia. More recently rising sea level at the end of the ice age isolated populations in Island Southeast Asia and led to human extinction in many places. This opened the way for the Austronesian people’s expansion once they had further developed their boating technology. Another example of a migration route once used being used several times.

Indo-Pacific and Pama-Nyungan

Language relationships within Australia and New Guinea provides further evidence that the progressive improvements in technology that allowed the gradual human expansion into the Pacific (see Part II) was simply a continuation of earlier patterns in the region.

Australian languages are usually divided into two distinct families: “Pama-Nyungan”, widespread in Australia, and, demonstrating amazing flair and originality, “Non-Pama-Nyungan” confined just to the continent’s northwest. They each show a huge level of diversity, presumably indicating a long period of diversification. This division into two language families almost certainly indicates two separate migrations although Josephine Flood (1988) says the two language families probably derive from a single ancestral language. The name Pama-Nyungan is a combination of the words for “one man” from the northeastern and southwestern ends of Australia and for many reasons it is presumed to be the earlier language family in Australia. The Non-Pama-Nyungan languages were introduced more recently.

On the other hand New Guinea had more prehistoric contact with the outside world (Howe 1984). It has a huge number of languages in at least three separate families.

I mentioned in “Pacific Population” [Mixing] that one branch of the Austric language family, Austronesian, was introduced to several coastal regions of New Guinea. Is it possible that some of the other, older languages are related to one or both Australian families?

Most languages of New Guinea are classified into one large sub-family: the “Trans New Guinea Phylum”. This is classified as part of the “Indo-Pacific family”. As I said in “Polynesian Origins” [Language Families] the languages of the Andaman Islands and the extinct Tasmanian language also belong to this family. All the non-Austronesian languages found in Melanesia beyond New Guinea also belong to the Indo-Pacific group (Howe 1984). This tends to further support the idea their boating ability was superior to that of the earlier migrants. They were able to reach further into the islands. We can presume this improved boating technology was also carried north and west back into Asia (and possibly as far as Central America? And what about Africa?). It is my guess the Indo-Pacific languages were widely spoken through Southern China and Southeast Asia before being replaced from about 10,000 years ago by the Austric language expansion (“Polynesian Origins” [Taiwan]).

Cavalli-Sforza et al (1994) suggests there may be some ancient relationship between these Indo-Pacific languages of New Guinea / Melanesia and the Non-Pama-Nyungan languages found in Northwestern Australia. This makes sense to me.

Around 35,000 to 25,000 years ago there was a decline of rainforest and an expansion of scrub steppe in Australia. This may have been due to climate deterioration but seems to be a greater decline than in similar previous events. It may be related to the final extinction of the large herbivores and a further increase in fires (“Extinctions” [How did we do it?]). And humans seem to have first reached New Britain, New Ireland and the Northern Solomon Islands (Western Melanesia) about 30,000 years ago.

That the Indo-Pacific languages of the Trans New Guinea Phylum arrived in New Guinea via the Sahul Shelf is supported by the fact they tend to be found to the south of the central mountain chain. They are present north of the mountains where it has been relatively easy to cross through mountain passes. I suspect the Indo-Pacific languages have largely replaced a third New Guinea language family, the “Sepik-Ramu group”.

Cavalli-Sforza (1994) goes on to suggest this Sepik-Ramu group, confined to the island’s extreme northeast, may represent remnants from an even earlier language. The original population that had passed through New Guinea on their way to Australia probably spoke this language. If we accept this possibility the Sepik-Ramu group would have a connection with the ancient Pama-Nyungan languages of Australia.

Explanation

This, then, is the defence’s explanation for the above evidence:

The ancestors of the first Australians moved down the eastern coastal regions of Asia from the north. Their technology already included some basic boating ability which allowed the proto-Pama-Nyungan / Sepik-Ramu people to be the first onto the closer islands. They reached New Guinea and Australia some time between about 70,000 and 50,000 years ago. They probably carried Y-chromosome line C and mtDNA line N and her descendant R’s daughter line P. The fossils found at Lake Mungo represent this physical type.

About 30,000 years ago Indo-Pacific, or Non-Pama-Nyungan-speaking, people were able to expand from further south into islands in the area today covered by the Arafura Sea (Sahul Shelf). People in the region had improved the boating technology the earlier immigrants had brought in. Their economy had become primarily coastal, swamp, lake and river. They carried mtDNA lines M and Q and Y-chromosome line K. The Kow Swamp fossils represent this type.

The defence suggests the two migrations into Australia / New Guinea were actually simply separated by the slight rise in sea level that occurred between about 50,000 and 30,000 years ago. The second movement from Southeast Asia must in turn have been completed before the recent rise in sea level that started about 10,000 years ago. My feeling is that there was intermittent migration from 30,000 years ago.

Map 17 shows the order of movements into Australia and New Guinea. It is based on both the third principal component of genetic distribution in Australia and the second principal component for New Guinea (Cavalli-Sforza et al 1994). The shaded area represents the genetic pattern derived from these two maps. This construction may be evidence for a second migration into Australia and New Guinea that arrived in the region of the Arafura Sea at a time of low sea level. During ice ages the Arafura Sea would have been dry land, or at least a series of islands and during wet periods many large lakes, ideal for boating, form through Central Australia. The second principal component for Australia (not shown here) reinforces the idea of a genetic movement into the Northwest of Australia.

Cavalli-Sforza’s maps don’t provide any genetic information for the Melanesian islands and so they are not shaded but I suspect they should be. Tasmania is not included in the pattern either. The pre-European population is extinct but they were considered to be more Melanesian looking than are the people from mainland Australia. For example they had tight, curly hair rather than long, wavy hair. This difference is easily explained by the interpretation of the evidence offered here.

More Evidence

The central genetic area of Australia in map 17 also coincides reasonably well with the distribution of stone points (including pirri points). Their distribution probably shows there is an established route of movement down through the centre of Australia during moister periods. The pirri points were introduced about 5000 years ago (Flood 1988) and indicate a technological spread rather than genetic. Their introduction is probably related to the spread of people south from Taiwan and the dingo’s introduction mentioned in “Pacific Population” [Mixing].

At the same time Austronesian languages were introduced to many Melanesian islands (“Polynesian Origins” [Language Families]). But genetic evidence cannot distinguish groups speaking the two language families. In spite of the very different languages gene flow has obliterated any original genetic difference. All this is further evidence in support of the wave theory of our evolution.

In “Pacific Population” [Mixing] the defence showed how the Polynesians were basically a hybrid of populations from the two eastern points of the human star. The jury has now seen that people in the Australian point were in turn the product of a complex mixture of human migrations. By now we have even been able to trace many of these migrations right back to and even beyond our origin as a species and we are but a short step from history. We will soon be able to use the wave theory to help us understand the beginning of that history, especially the connections and contradictions between what the Old Testament of the Bible and what the wave theory tells us. And as we now follow European history from the Upper Paleolithic until today the jury will see that the processes that led to our evolution from Australopithecus to Homo erectus continue. But before we sneak back and have a look at the origin of the northern part of the mix we need to understand the evolution of culture.

Witnesses Called

Adcock et al (2001) Mitochondrial DNA Sequences in Ancient Australians. Proc. Natl. Acad. Sci. Vol. 98 pp. 537-542.

Cavalli-Sforza, Luigi Luca, Menozzi, Paolo and Piazzi, Alberto (1994) The History and Geography of Human Genes. Princeton University Press, New Jersey.

Curtis, Garniss, Swisher, Carl and Lewin, Roger (2001) Java Man. Little, Brown and Company, London.

Flood, Josephine (1988) Archaeology of the Dreamtime. Collins, Australia.

Howe, K. R. (1984) Where the Waves Fall. George Allen and Unwin, Australia.

Jennings, Jesse D. (1979) The Prehistory of Polynesia. Australian National University

Press, Canberra.

Mellars, Paul ed. (1990) The Emergence of Modern Humans. Edinburgh University

Press, Great Britain.

Olson, Steve (2002) Mapping Human History. Houghton Mifflin Company, New York.

Stringer, Christopher and Gamble, Clive (1993) In Search of the Neanderthals. Thames

and Hudson, Great Britain.

Stringer, Christopher and McKie, Robin (1996) African Exodus. Random House, UK.

Early Aztec Pyramid Found in Tlatelolco, Central Mexico City

Known locally as the Plaza de los Tres Culturas, a dismal setting for tourists, and a lethal one back in 1968, when 300 students were gunned down during a demonstration there, this location in Mexico City, known in the past as Tlatelolco, has something of a chequered past, with the bloodbath of 1968 becoming a faint echo of an even worse atrocity which took place there back in 1521, when it is estimated that 40,000 inabitants were slaughtered in a single day at the hands of the Spanish conquistadors, led by Hernán Cortés.

On a slightly brighter note comes news of the discovery of a pyramid there, described for us here by Reuters...

Archeologists have discovered the ruins of an 800-year-old Aztec pyramid in the heart of the Mexican capital that could show the ancient city is at least a century older than previously thought.

Mexican archeologists found the ruins, which are about 36 feet (11 metres) high, in the central Tlatelolco area, once a major religious and political centre for the Aztec elite.

Since the discovery of another pyramid at the site 15 years ago, historians have thought Tlatelolco was founded by the Aztecs in 1325, the same year as the twin city of Tenochtitlan nearby, the capital of the Aztec empire, which the Spanish razed in 1521 to found Mexico City, conquering the Aztecs.

The pyramid, found last month as part of an investigation begun in August, could have been built in 1100 or 1200, signalling the Aztecs began to develop their civilization in the mountains of central Mexico earlier than believed.

"We have found the stairs of this, much older pyramid. The (Aztec) timeline is going to need to be revised," archaeologist Patricia Ledesma said at the site on Thursday...

...Ledesma and the archaeological group's coordinator, Salvador Guilliem, said they will continue to dig and study the area next year to get a better idea of the pyramid's size and age.

The archeologists also have detected a sculpture that could be of the Aztec rain god Tlaloc, or of the god of the sky and earth Tezcatlipoca.

In addition, the dig has turned up five skulls and a series of rooms near the pyramid that could date from 1431.

"What we hope to find soon should tell us much more about the society of Tlatelolco," said Ledesma.

Mexico City is littered with pre-Hispanic ruins. In August, archeologists in the city's crime-ridden Iztapalapa district unearthed what they believe may be the main pyramid of Tenochtitlan.

One of the great losses to archaeology, and indeed the Aztecs, was the complete destruction of the ancient city of Tenochtitlan, as can be gathered from this description...

"Tenochtitlan," as the Aztecs called the metropolis at the heart of their tribute empire, has always had the capacity to astonish outsiders. The first Europeans to see it were the small band of Spanish adventurers led by Hernan Cortès who were to become its conquerors. As they crossed a snowy pass into the shallow cup of a wide valley in central Mexico late in November 1519, they saw a sight they could not easily believe.

A great white city, lightly moored to the shores by three long causeways, floated on a shimmering lake. The last city they had seen was Seville, the largest in Spain, sheltering more than sixty thousand souls. This lake-borne city was almost four times as large, with thousands more people clustered in the "suburbs" fringing the mainland.

And this city, unlike the cramped muddle of houses, streets, and byways that made up medieval Spanish towns, had been planned. Its habitations were neatly packed within a ruler-straight grid of canals and footpaths, so Cortès and his men could see four processional ways converging on a central precinct where temples and pyramids rose in the morning air like man-made mountains.

No encrustations of smoke or dirt sullied these fairytale structures: they were brilliant with colored stuccos, and even the humblest dwellings, some of them crested with roof-gardens, shone with whitewash.

In old age, Bernal Diaz, a Spanish foot-soldier in that long-ago campaign and still our best and most engaging witness, remembered the impact of the "enchanted vision" of the magical city, with its "pyramids and buildings rising from the water . . . Indeed, some of our soldiers," he reported, "asked whether it was not all a dream."

For the inhabitants of Tenochitlan, the arrival of the Europeans turned out to be a terminal nightmare from which they never awoke.

image : El Mercado de Tlatelolco - Mural de Diego Rivera, from here

TED | Talks | Carolyn Porco: Fly Me To The Moons of Saturn (video)

Following on from the previous post in which looked at whether or not it's a good idea for humanity to advertise its presence to alien civilisations that may or not exist, and may or not be kindly disposed towards us, here's a video which looks at humankind's current endeavours to explore our solar system by deploying robotic missions to the various planets, moons and other bodies, such as Pluto, which comprise our solar neighbourhood.

Carolyn Porco here gives us a progress report of the Cassini-Huygens Mission to Saturn, and in this talk focuses on what has been discovered regarding 2 of Saturn's 47 moons, namely Titan and Enceladus, since the mission's arrival in the outer solar system, describing the surprising features that have been found there.

Before Cassini arrived, it had been impossible to see through the global haze over Titan, but we have since learned from the mission that methane on Titan is as ubiquitous as water here on Earth, and despite the incredibly low temperatures there, methane stays liquid, with rain, lakes and rivers carving out various parts of the landscape there - it's further thought there may be tectonic activity there, and the highpoint of this part of the mission was the deployment of the Huygens probe that made it down to the surface of Titan, and is referred to by the speaker as the culmination of a truly international effort.

The biggest surprises were on Enceladus, where it was discovered that the fracturing seen on its southern surface were a coating of 'organic materials' - and that it's south pole was the warmest point on the moon. The images of the plumed jets are thought to be ejecting from pockets of liquid water there, and along with the heat, strongly indicate that life might be supported there - which if true, and assuming that some sort of life did, or still does, exist on Mars, would make three locations within our very own solar system where life has taken hold.

As we saw in the preceding post, the mediocrity argument would appear to be very well expressed here - if at least three bodies in this solar system have life, intelligent or otherwise, the odds of life existing elsewhere in the galaxy and at other locations across the Universe, may well have shortened dramatically.

Seed: Who Speaks for Earth? - David Grinspoon

An article by David Grinspoon, discussing the attempts by Alexander Zaitsev, Chief Scientist at the Russian Academy of Sciences' Institute of Radio Engineering and Electronics, to establish contact with what he hopes are alien civilisations living elsewhere in the galaxy, in a venture known as Active SETI. His efforts have drawn criticism from others who contend that as we have no idea whether these putative civilisations are friendly or hostile, it would be better if we remained silent, just in case someone or something decides to pay us a visit we might regret or even not survive.

For years the debate over Active SETI versus passive "listening" has mostly been confined to SETI insiders. But late last year the controversy boiled over into public view after the journal Nature published an editorial scolding the SETI community for failing to conduct an open discussion on the remote, but real, risks of unregulated signals to the stars. And in September, two major figures resigned from an elite SETI study group in protest. All this despite the fact that SETI's ongoing quest has so far been largely fruitless. For Active SETI's critics, the potential for alerting dangerous or malevolent entities to our presence is enough to justify their concern.

"We're talking about initiating communication with other civilizations, but we know nothing of their goals, capabilities, or intent," reasons John Billingham, a senior scientist at the private SETI Institute in Mountain View, California. Billingham studied medicine at Oxford and headed NASA's first extraterrestrial search effort in 1976. He believes we should apply the Hippocratic Oath's primary tenet to our galactic behavior: "First, do no harm."

For years Billingham served as the chairman of the Permanent Study Group (PSG) of the SETI subcommittee of the International Academy of Astronautics, a widely accepted forum for devising international SETI agreements. But despite his deep involvement with the group, Billingham resigned in September, feeling the PSG is unwisely refusing to take a stand urging broad, interdisciplinary consultation on Active SETI. "At the very least we ought to talk about it first, and not just SETI people. We have a responsibility to the future well-being and survival of humankind."

We next look at the SETI Protocols - the first of which addressed the issue of how Earth should go about replying to any message received from an extraterrestrial source, and this involved consultation with all the nations on the planet before any reply was sent. The second, formulated at a meeting in Valencia, 2006, dispensed with the idea of involving other nations, with Seth Shostak stating that SETI has no right to dictate policy to the rest of the world.

But Michael Michaud and John Billingham disagree, saying that SETI should be open and transparent, and that potential contact with sentient beings from elsewhere should be discussed amongst a broader spectrum of scientists, and not just take place within the ranks of SETI, who are after all, funded by tax dollars.

With the current state of world politics, fundamentalist religious conflict and associated warfare, widespread disease and poverty, it's unlikely that the nations of the world could unite and agree on a specific response to ET - which also might raise the question of how we respond to different groups of aliens, who themselves might hold widely differing views on life and the Universe in general, inter alia.

The assumption is commonly made that any aliens we do contact will be representative of their entire race, holding common beliefs and aims - whereas if their worlds are in anything like the same state as our own, will mean that we would need to address completely different sets of issues when conducting diplomatic exchanges with different aliens, who might well be in a state of war or political/religious/economic conflict with one another.

Seth Shostak further believes that public discussion of rules for contacting ET would bring SETI bad publicity, and with it a possible lack of funding - every researcher's nightmare, because without public funding, operations would effectively cease. And although it's easy to sympathise with those who call for complete openness at SETI, I think Shostak is also partly correct in attempting to keep a lid on things as far as the rest of the world is concerned, as any attempt to compose a global message would take years of argument and compromise, and wouldn't be able to reflect the views of all humankind anyway.

But it would appear to be prudent to involve the wider scientific, academic and religious communities, at least to the degree where they can offer what would hopefully be constructive input to the debate. However, many would argue that in this instance science and religion should be kept apart, especially when it might be discovered that humankind wasn't the only (intelligent) life, or sole creation of God, in the Universe. However, religious leaders might well have to address their own congregations in the future regarding the discovery of other life from elsewhere, and it could be argued that to some extent they should be kept in the loop.

Back to the article...

Long before he was an eager practitioner of Active SETI, Alexander Zaitsev was already a respected astronomer investigating planets using huge blasts of radar energy from the 70-meter radio telescope at the Evpatoria Deep Space Center in Crimea, Ukraine. Planetary radar studies rely on powerful, focused beams to "illuminate" distant objects, though much of this energy misses its target. The beams would be fleeting if seen from other stars that, by chance, lay along their path. But aimed and modulated to contain pictures, sounds, and other multimedia, they very easily become calling cards from Earth. On balance, it's relatively simple to send signals, so why have we just been listening?

SETI doctrine states that anyone we hear from will almost certainly be much more advanced than we are. Simply put, our capabilities are so rudimentary that any chance of detecting an alien transmission would require that it be broadcast powerfully and continually on millennial timescales. We can't predict much about alien civilizations, but we can use statistical mathematics to derive simple, robust relationships between the number of putative civilizations, their average longevity, and their population density in the galaxy. The chance of getting a signal from another baby race like ours is infinitesimally small. As Shostak says, "We've had radio for 100 years. They've had it for at least 1,000 years. Let them do the heavy lifting."

Michio Kaku, in a recent interview with Art Bell, (clips available here) believes that for intelligent life and/or a civilisation to have arisen, the beings involved would most likely have had to been predatory, as a predator is supposedly more intelligent than the prey it pursues, and he further believes that those same predatory instincts could well dictate policy when it comes to establishing contact with other civilisations such as ourselves.

Our search of the heavens has recently been augmented by the 350-strong Allen Telescope Array, which has increased our ability to scan stars for radio signals a thousand-fold, and the Kepler mission due to launch next year will examine maybe 600 planets for tell-tale signs of life, in the same way as the COROT satellite is currently doing and this will direct the SETI effort. Kaku reckons we are entering a golden age of space exploration, and even believes there is few percent chance of us detecting radio transmissions from other beings in other solar systems.

Commenting on the SETI Protocols, he believes that contact with intelligent life should be a matter of national security, and as such kept from the public, rather than go for the freedom of speech approach - he quoted Arthur C. Clark, who once opined that there either was intelligent life elsewhere in the Universe, or there wasn't - either thought is equally frightening.

Kaku doesn't believe we should advertise our presence to these putative aliens, although he reckons they wouldn't come visiting to eat us, or to plunder our planet for its natural resources, and may even just travel here out of curiosity. However, we cannot hide our presence here, due to the waste radiation that emanates from Earth, not least in the form of radio and TV transmissions which are constantly being produced.

Michio Kaku often makes the point of how some of our earliest TV transmissions - which might be picked up aliens looking out for them - would be 'I Love Lucy', but even earlier TV broadcasts came out of Nazi Europe back in the 1930s, and it's difficult to gauge how aliens might react to seeing either of these transmissions as their first impression of humankind - although seeing the two together would actually give an accurate snap-shot of at least one characteristic of humankind's cultural preferences - obsessed by war and soap-operas in equal measure.

Whether they would then come running to greet us, or chose to ignore us after seeing such broadcast material is a moot point, and it's possible they may consider us to be too primitive or backward to be of any interest or constructive use to the wider galactic community.

So far, these signals could only have travelled out a distance of 50 light years, whereas it's possible that earlier galactic civilisations could have been emanating radiation of thousands or even millions of years, presumably making it more likely that we detect them before anyone detects us. More from David Grinspoon...

What if there is something dangerous out there that could be alerted by our broadcasts? This ground has been explored in numerous scientific papers and, of course, in countless works of science fiction. Few people alive today embody the convergence of hard science and fictional speculation better than David Brin, an author of both peer-reviewed astronomy papers and award-winning science fiction novels. In an influential 1983 paper titled "The Great Silence," Brin provided a kind of taxonomy of explanations for the lack of an obvious alien presence. In addition to the usual answers positing that humanity is alone, or so dull that aliens have no interest in us, Brin included a more disturbing possibility: Nobody is on the air because something seeks and destroys everyone who broadcasts. Like Billingham and Michaud, he feels the PSG is dominated by a small number of people who don't want to acknowledge Active SETI's potential dangers.

Even if something menacing and terrible lurks out there among the stars, Zaitsev and others argue that regulating our transmissions could be pointless because, technically, we've already blown our cover. A sphere of omnidirectional broadband signals has been spreading out from Earth at the speed of light since the advent of radio over a century ago. So isn't it too late? That depends on the sensitivity of alien radio detectors, if they exist at all. Our television signals are diffuse and not targeted at any star system. It would take a truly huge antenna—larger than anything we've built or plan to build--to notice them.

Alien telescopes could perhaps detect Earth's strange oxygen atmosphere, created by life, and a rising CO₂ level, suggesting a young industrial civilization. But what would draw their attention to our solar system among the multitudes? Deliberate blasts of narrow-band radiation aimed at nearby stars would—for a certain kind of watcher—cause our planet to suddenly light up, creating an obvious beacon announcing for better or worse, "Here we are!"

First, a quick look at David Brin's paper, 'The Great Silence' (pdf) , which addresses some of the issues, under the heading of 'Philosophical Issues' thus...

The SETI debate is unique. To no other subject do modern scientists bring a more eclectic array of speculations, combining biology, chemistry, sociology and astrophysics. In no other area do philosophical issues butt heads so dramatically.

For instance, the Cosmological Principle, or 'assumption of mediocrity' is taught almost as religious canon to students of astronomy. Since Copernicus removed the Earth from the centre of the cosmos, astronomers have come to hold in suspicion any theory that proposes that our time and place is anything but mundane and mediocre. Again and again, as our conception of the Universe has expanded, this principle has proved rewarding.

It seemed natural to exobiologists of the 1960s to extend the concept of mediocrity from purely physical situations to evolution here on Earth...the implication being that the local occurrence of life, and even intelligence, must merely be a typical case of a common phenomenon.

(Had the Viking mission verified even modest Martian micro-organisms deriving from an independent genetic heritage, SETI proponents would have had cause for encouragement. The mediocrity argument would have gained support. But it is impossible to extrapolate from a single data point.)

Regarding that last bracketed comment, it now transpires that not only might there well be abundant water on Mars, and possibly extant life, the Viking missions of 1976, referred to by Brin in 1983, might have made just such a discovery, as we see from this recent article at New Scientist Space...

A flawed test on NASA’s twin Viking spacecraft may have fooled scientists into overlooking signs of life during their examination of the Martian surface 30 years ago. Researchers now say that one of the landers’ experiments was not sensitive enough to find organic molecules in the soil, despite signs of life shown by another test. Other researchers say the team may also have been fooled by the strange forms that Martian life might take.

The results from Vikings’ onboard experiments are confusing because some tests suggested the presence of organisms capable of digesting organic molecules. But a gas-chromatograph mass spectrometer (GCMS) found nothing when the soil was heated to release organic molecules, causing most scientists to doubt the results of the life-detection tests. Instead they put the soil reactivity down to the presence of peroxides or other reactive substances.

Now, a paper by Rafael Navarro-Gonzalez of the University of Mexico and others demonstrates that the GCMS instrument was incapable of detecting organic compounds even in Mars-like soils from various locations on Earth. This includes parts of Chile's Atacama desert where other tests prove that living microbes are indeed present.

In some soils – including samples taken from Rio Tinto in Spain, which contain iron compounds similar to those detected in Mars soils by NASA's rover Opportunity, the sensitivity of the GCMS was actually a million times lower than its claimed threshold for detection, says Navarro-Gonzalez.

So the SETI proponents may well have been entirely justified in their expressed beliefs some 30 years ago, although at the time there was a general move away from funding space projects, which had even seen the Apollo lunar programme being curtailed before all the planned missions had been completed.

Another canonical aspect of our consideration of other civilisations is that they will always be far more technologically advanced than ourselves - or at least those with whom we establish contact. But by extrapolating the mediocrity principle. we could equally assume that although there are other civilisations out there, at a similar stage of technological development as ourselves, and they may be just as isolated as ourselves, too far away from anyone else ever to detect, let alone establish communications or go visiting. Here's a quote from a related essay at Centauri Dreams...

One reason our SETI searches may be turning up nothing is that everywhere in the cosmos, civilizations exist that are much like ours. They may be, in other words, what Alexander Zaitsev calls ‘dismally monotonous,’ capable of being no more than passive when it comes to other living worlds. They are listening rather than transmitting. And Zaitzev is at the forefront of the movement to change all that, at least where Earth is concerned.

Zaitsev’s new paper lays out the basics of METI — ‘Messaging to ETI’ — the idea being to transmit purposely to likely stellar systems. The Russian scientist is fascinated by the question of consciousness. How widespread is it, and is it not the aim of SETI to find out whether it is a universal phenomenon or a singular one, isolated on our own world? On this score, all kinds of speculation are possible, and I rather like this Arthur C. Clarke quote cited by Zaitsev as one of various hypotheses:

“…it is almost evident that biological intelligence is a low form of intelligence. We are at the early stage of the evolution of intelligence, but at the late stage of the evolution of life. True intelligence is unlikely to be living.”

But of course, we don’t know that, nor do we know how to regard John Wheeler’s ‘participatory anthropic principle,’ which says that it takes observers to bring the universe into being. Zaitsev thinks that true participation in the universe requires something more than contemplation, and that we should supplement Wheeler with this thought: ‘Senders are necessary to bring consciousness into the universe.’

Here's the introduction to the METI paper...

Those who propose, or oppose, sending Messages to Extra-Terrestrial Intelligence (METI) must contemplate the Hamlet-like question: “To send or not to send?” The science known as SETI deals with searching for messages from aliens. METI science deals with the creation of messages to aliens. Thus, SETI and METI proponents have quite different perspectives. SETI scientists are in a position to address only the local question “does Active SETI make sense?” In other words, would it be reasonable, for SETI success, to transmit with the object of attracting ETI’s attention?

In contrast to Active SETI, METI pursues not a local, but a more global purpose – to overcome the Great Silence in the Universe, bringing to our extraterrestrial neighbors the long-expected annunciation “You are not alone!”

Thus, it follows that in the context of METI, the answer to the general question of transmissions from Earth requires competence beyond the membership of the highly specialized SETI Permanent Study Group of the International Academy of Astronautics (IAA-SPSG). We therefore propose that, for solution to the various current METI problems, we establish both a METI Institute, and METI Permanent Study Group within the IAA (an IAA-MPSG).

Of course, the underlying question to establishing contact with alien civilisations is what do we as the human race hope to gain by all this? If we made contact with a people technologically far in advance of ourselves, we'd quite naturally want to benefit from their knowledge in order to better the lot of humanity, in the hope that we might solve our energy and natural resource problems which are beginning to assume alarming proportions, especially in the context of terrestrial eco-systems and global climate being in a state of decreasing stability, whether caused by humankind or not.

But such gains by humans in technological knowledge would probably remain in the hands of the global corporations, and it's unlikely that the majority of the world's population would benefit in the short term. And given our bellicose nature, it's likely that an advanced civilisation would have grave doubts about entrusting us with powerful technologies that would increase our destructive capabilities far beyond anything we can currently contemplate - plus it's likely we would have little in the way of stuff worth trading to an extra-terrestrial civilisation that might want recompense for divulging such secrets as the ability to traverse vast swathes of space within the lifetime of a human, or anti-gravity capabilities, or even the ability to stay alive for centuries or millennia, in a life free of ageing, illness or disease.

In short, it is likely we would demand far more of our alien contacts than they would of us, and our sole aim might then be to become as powerful as them, if not more so. But technological aspirations aside, there is a great deal we might otherwise learn from other people dwelling on other worlds, not least our theory of evolution, and how humankind came to be.

Bearing in mind our quite limited knowledge of how we, along with all life on this planet, came to exist at all, let alone evolved into the myriad of lifeforms that have existed here over the past few billion years, it would be interesting indeed to learn how intelligent life has arisen elsewhere. Maybe an advanced civilisation would have worked out each step of their previous existences of evolved life over the course of millions of millennia, and understand exactly how life had started, progressed and prevailed - or indeed, whether they were just as puzzled as ourselves as to how the essence of life manifested itself in the first place - and whether they held any religious or creationist beliefs similar to those held by many humans today, in which an almighty super-being created the whole, ex nihilo.

Many would be interested to know how other intelligent life might investigate its own (pre)history, and how they have come to know what they do about their own past, or whether they even consider such research to have any validity - do alien archaeologists go around opening up trenches to discover fossilised versions of their former selves, replete with artefacts made by forebears who are to them as mysterious as ours are to us?

Here's a final word from David Grinspoon...

So far SETI has turned up no evidence of other intelligent creatures out there seeking conversation. All we know for certain is that our galaxy is not full of civilizations occupying nearly every sun-like star and sending strong radio signals directly to Earth. In the absence of data, the questions of extraterrestrial intelligence, morality, and behavior are more philosophy than science. But even if no one else is out there and we are ultimately alone, the idea of communicating with truly alien cultures forces us to consider ourselves from an entirely new, and perhaps timely, perspective.

Even if we never make contact, any attempt to act and speak as one planet is not a misguided endeavor: Our impulsive industrial transformation of our home planet is starting to catch up to us, and the nations of the world are struggling with existential threats like anthropogenic climate change and weapons of mass destruction. Whether or not we develop a mechanism for anticipating, discussing, and acting on long-term planetary dangers such as these before they become catastrophes remains to be seen. But the unified global outlook required to face them would certainly be a welcome development.

It should come as no surprise that we as a species are casting our telescopic eyes out across the vastness of space in the hope of finding someone else with whom to communicate, and it might just be to the benefit of ourselves to act for once as a united global community in endeavouring to understand the context of our planet and ourselves as being something that for all we know might be unique in all the Universe, and something worth making the effort to preserve rather than continuing along a path of ignorance and animosity that will surely visit destruction upon us more surely and quickly than any putative alien civilisations.

It could be argued that we are not yet culturally ready to take the step into the great beyond, and on current form, it may be many hundreds or thousands of years before we have solved our own problems to the extent that we could actually contribute something to a wider space community, rather than merely use it as a resource from which to download important upgrades to our own rather limited operating systems.

see also: Dr. Alexander Zaitsev : Sending And Searching For Interstellar Messages

David Brin, 2002 - A Contrarian Perspective of Altruism:The Dangers of First Contact - pdf

image of ATA from here

Dr. Mark Aldenderfer Appointed as New Editor of 'Current Anthropology' - The Wenner-Gren Foundation

Although it's likely that most other readers of Current Anthropology will already be aware of this news, it's something that only just caught my eye, and seems noteworthy enough to merit quoting here in full...

The Wenner-Gren Foundation and University of Chicago Press are pleased to announce that Mark Aldenderfer has been selected to succeed Benjamin Orlove as the 6th editor of Current Anthropology. The Foundation thanks Dr. Orlove for his successful leadership of eight years and welcomes Dr. Aldenderfer in his new role as editor of Current Anthropology.

Currently professor of anthropology at the University of Arizona, Aldenderfer is an archaeologist with extensive field experience in North and Central America, the Andes, the Tibetan plateau, and Africa, and works primarily with ancient hunting and gathering peoples. His varied research interests include the emergence of social inequality, the archaeology of religion, and the comparative analysis of high altitude cultural and biological adaptations. He is especially interested in digital approaches to field work and publication and quantitative methods as applied to anthropological questions.

He brings to Current Anthropology extensive editorial experience. He is presently co-editor of Latin American Antiquity, and served as the editor of the Society for American Archaeology Bulletin, then SAA Archaeological Record, for nine years. He has edited or co-edited seven books on a variety of topics, was a co-editor of a series of books on archaeology for the Greenwood Publishing Group, and is an Advisory Editor and member of the Steering Committee of Internet Archaeology, the first successful online peer-reviewed journal in the field.

Aldenderfer will take up the editorship in January 2008.

This blog wishes him all the best in his new position.

Dr. Mark S. Aldenderfer

Current Anthropology

Neanderthals' Lack of Sewing Skills Blamed on Their Extinction

Whilst we know that Neanderthals ceased to exist as a viable species some 25,000 years ago, there is still no clear, single cause that can account for their disappearance, and one of the reasons an answer has been hard to come by, is that too many studies have focused on trying to present a single or specific factor that was responsible for their demise, untimely or otherwise. The most recent comes from Ian Gilligan, of the Australian National University, as described at ABC Science, who report on his paper published in World Archaeology...

Neanderthals probably froze to death in the last ice age because rapid climate change caught them by surprise without the tools needed to make warm clothes, says an Australian researcher.

Neanderthals began to die out just before the last glacial maximum, 35 to 30,000 years ago and were replaced by modern humans, say archaeologists.

Previous studies have argued that one of the key reasons for this is that modern humans had better hunting tools, providing them with the extra food they needed to survive the cold.

But Gilligan disagrees that the development of hunting tools was so important to modern humans' survival over the Neanderthals.

For a start, he says, Neanderthals were already successful hunters, surviving in Europe and Eurasia for over 100,000 years.

Neanderthals actually prevailed for far longer, probably about 300,000 years, and maybe back even further - moreover, by the time of the Middle/Upper Palaeolithic transition, they had lived through the previous ice age, with or without clothes, and had evidently not frozen to death in the process.

The important tools developed by modern humans included stone blades, bone points, and later needles, which could cut and pierce hides to sew them together into multi-layered clothes including underwear, says Gilligan.

"They're not related to hunting, they're related to clothing," he says. "These tools are related to tailored, fitted clothing, what I call complex clothing."

He says modern humans were more vulnerable to the cold than Neanderthals and developed these tools as far back as 90,000 years ago to cope with cooler parts of Africa, before the peak of the ice age.

"This made them pre-adapted to the glacial maximum," says Gilligan.

But Neanderthals were physically more resistant to the cold, he says.

Because of this they were quite happy before the ice age to get around in similar temperatures wearing little less than single-layered loosely-draped animal hides.

This gave Neanderthals no pressing need to develop complex clothing, says Gilligan.

But when the peak of the ice age came, it was a shock.

We don't know how easily Neanderthals were shocked or surprised, or indeed how they were adapted to react to same, but in any case, the glacial maximum didn't occur till around 20,000 years ago, long after the Neanderthals supposedly breathed their frosty last. They had lived through changing climate events before, although in the previous glaciation there had been no anatomically modern humans living in Eurasia.

But the points the author raises regarding the apparent inability of Neanderthals to sew clothes together, don't seem to take into account another vital facet of making clothes from animal hides, that being the importance of knowing how to dry and prepare such material so that it doesn't simply decay and rot, making it unsuitable for clothing of any type.

Here's a brief passage from 'Hunters of The Stone Age', by Dr. Karel Sklenář, from Chapter 4, 'Clothes', which offers a generalised look at early use and treatment of animal skins...

"Even before Homo sapiens evolved, earlier species of (humans) had probably realised that an animal skin could be used for various purposes. Perhaps one of the earliest uses to occur ...was as clothing. If animals are covered in hairy skin...why should not man wrap himself (or herself) in the same skins?....

...If an animal skin is not properly treated and prepared it will soon become useless for clothing and quickly fall to pieces. Exactly when (humans) realised what (they) had to do to avoid this we simply do not know, but by the Late Palaeolithic a whole range of tools had emerged to make skins softer, finer and more durable.

The process involved was lengthy and meant much work, First, strong, stone knives were used to remove the skin from the animal. The hide was then stretched out either on a frame or on pegs driven into the ground. Tools known as scrapers were used next.

These were made of stone and had only one edge, which was used to scrape fat and underskin ligaments from the hide. Smaller scrapers, sometimes small flint splinters set in wood, were used to remove the final traces of fat and ligament. Finally, bone smoothers were used to work the skin, smoothing it out and making it more supple."

The text then goes on to describe the sewing process, and there can be little doubt that this invention was a mighty one indeed, as it allowed for a much greater precision in the manufacture of clothing, and doubtless was instrumental in Upper Palaeolithic people looking much smarter and well turned out than any of their archaic predecessors, although those same ancestors may have opined that their modern counterparts merely looked overdressed for every occasion.

It seems likely that Neanderthals had the necessary stone tools and survival skills to be able to modify and exploit animal skins to at least stabilise them enough to be used as clothing, and probably designed them a lot more efficiently than often depicted in modern-day artistic impressions, which tend towards a single pelt of fur draped casually over the shoulders, providing little protection against anything at all.

But tailored clothes may not have been necessary as part of a cold weather survival kit - for example, we know that up to 50% of body heat is lost through the head, so a good hat could have made a significant improvement to the chances of survival in extreme cold, and you don't need an advanced sewing kit to produce effectively protective head gear.

It is also known that animal fat provides pretty good insulation against the cold, and a liberal smearing of such fats, which would have been natural by-products of cooked meats such as reindeer, would likely have been in ample supply. It is often suggested that Neanderthals were exceptionally hirsute, and although there is no scientific evidence for this, being hairy may have been an advantage, as the applied layers of animal fat to keep warm would have stuck more readily to a good matting of body hair than smooth skin. Inelegant, admittedly, and the wearers would doubtless have smelled fairly ripe, but in matters of survival in a deep freeze, a sartorial dress sense was probably less than essential - at the very least, the appliance of fat would have saved them from chapped lips, which as we know, can be irksome to bear.

But even an ability to sew tailored clothing would not have been enough to stave off frostbite, which typically affects the extremities, with fingers and toes likely to fall prey to the intense chill of an deepening glaciation, no matter how well the rest of the body may have been wrapped in fancy furs and fitted skins, and it is likely that early modern humans in the Upper Palaeolithic, as their Neanderthal predecessors, would have been under considerable duress from this ever-present threat.

see also: Wikipedia - Châtelperronian

Hypothermia

Tunguska to Arecibo: The Greater Danger Posed By Smaller Asteroids

Earlier this year we heard how it has been suggested that the Clovis era in the New World came to an end when a comet exploded high over Canada, and may even have been implicated in the massive extinction of megafauna across the Americas.

We usually assume that such Earth shattering events are caused by fairly large objects travelling in from outer space, and today there are various bodies who watch out for asteroids that may be on a collision course with Earth, although what action we can take if we detect one that is inbound is at the moment very little.

But a recent study of the Tunguska event in 1908 has drawn some rather worrying conclusions, in that very destructive impact events might be caused by objects far smaller than we are able to detect. Originally thought to have been between 50-100 meters in diameter, new research suggests that the presumed asteroid that exploded in mid-air may have been much smaller, but greatly more efficient in scorching the Earth, which in turn suggests that it may be far more difficult to detect diminutive asteroids packing a similar punch.

Centauri Dreams has coverage of some recent research into the Tunguska event, the centenary of which will be on June 30th next year, and this latest article provides a timely reminder of yet another way in which humanity's survival could be under dire threat from circumstances beyond or understanding, let alone control, as we see in this excerpt from Tunguska to Arecibo - Connecting The Dots...

Fifteen megatons of TNT would set off a blast a thousand times more powerful than the weapon used on Hiroshima. 2000 square kilometers of flattened pine forest near the Podkamennaya Tunguska River in central Siberia bear witness to what such a blast can do. That explosion occurred on June 30, 1908 [original typo said ‘2008,’ an obvious mistake!], and we’re learning more about it.

The Tunguska event seems to have been an air blast occurring at an altitude between five and ten kilometers. The presumed cause: A small asteroid slamming into our atmosphere at speeds in the range of 15-30 kilometers per second. But just how big was the asteroid? I’ve seen estimates in the range of 50-100 meters in diameter, but we know surprisingly little about the object. No fragments exist.

The effects of the fireball and blast wave are apparent (and there are eyewitness accounts of hot winds and shaking buildings), but there is no crater at the epicenter of the blast. We’re left to calculate the parameters of the object through its effect and its presumed composition and speed as it entered the atmosphere.

New work at Sandia National Laboratories suggests something that is worrisome indeed. I’m going to let Sandia’s Mark Boslough deliver the bad news:

“The asteroid that caused the extensive damage was much smaller than we had thought. That such a small object can do this kind of destruction suggests that smaller asteroids are something to consider. Their smaller size indicates such collisions are not as improbable as we had believed… We should be making more efforts at detecting the smaller ones than we have till now.”

The Sandia work uses a supercomputer to match the known facts with their probable cause. The devastation delivered by the Tunguska object slammed into the ground in the form of a high-temperature jet of expanding gas.

The fireball turns out to be more efficient than we realized, creating a blast wave and thermal radiation at the surface stronger than would have been predicted simply by modeling an explosion at the assumed altitude. New models of the fireball show that the energy it transported to the surface is consistent with only a three to five megaton blast, much smaller than originally thought.

And as we see from the linked page at Sandia, the danger of being hit by something we are unable to detect is potentially greater because of the greater number of smaller asteroids which exist...

Because smaller asteroids approach Earth statistically more frequently than larger ones, he