Human Evolution on Trial - Chromosomes and DNA - by Terry Toohill

Human Evolution on Trial - 'Chromosomes and DNA'

Most members of the jury will have heard of genes and know they are responsible for our inherited characteristics. As you probably already know, your genes control such things as your skin, hair and eye colour, the shape and size of your face, eyes and nose, your blood group and to a large extent your general height and shape as well as many other things, such as elements of your personality (Steve Jones 2000). One of my brothers believes even the willingness, or otherwise, of individual dairy cows to come into the open side of a herringbone milking shed is inherited. Anyway it is most likely that instinctive behaviour is genetically inherited in some way. Humans have many instincts. One of them is the ability to learn a language (Ridley 2000). We’ll come back to language periodically.

Humans may have up to a hundred thousand genes although the precise figure is debated. Some say many less than half this number but, almost certainly, the complex interrelationships between genes are usually underestimated. A change in a single gene can have a huge effect. For example cultivated maize differs from its vastly different wild form in just five genes (Jobling et al 2004). The environment we are brought up in does affect the influence of our genes, and some evidence indicates it may influence the genes themselves, but we can ignore both of these possibilities for now.

Experiments have shown that genes for each of your characteristics occur in pairs, one of each pair from your mother and your father. If the two genes of a pair are different usually only one of them gives rise to your observed characteristics. This one is called the “dominant” gene. The other one remains hidden but can be passed on to any of your offspring. This gene is called “recessive”. The evidence shows that your genes are carried on your chromosomes, which are confined to the nucleus (the centre) of each cell of your body. Except for the Y-chromosome, chromosomes usually occur in pairs. In fact the jury will see that a hierarchy of pairing passes on genetic information.

Y-chromosome

Each single chromosome, of each pair, consists of a double string of DNA (deoxyribonucleic acid) mixed with proteins. DNA is actually a string of what are called nucleotides attached to a series of alternating sugars and phosphoric acid (technically the nucleotide is the combination of all three chemicals). Just four types of nucleotides are present in the chain. In DNA they are adenine, thiamine, guanine and cytosine or A, T, G and C. Each strand of DNA is a string of up to a hundred million of these four nucleotides in various sequences giving a total of about three billion for the total human genome (see for example Stringer and McKie 1996). In the paired strand of nucleotides in each chromosome the adenine in one strand is always joined by hydrogen bonds to thiamine in the other, and guanine in one is joined to cytosine in the other strand (A-T, G-C). This means that chromosomes are easily able to replicate themselves. When the double strand of DNA splits each separate strand must replicate the other strand. Therefore the two new chromosomes, or double strands of DNA, are exactly the same as the original chromosome. The defence has included drawings of dividing strands of DNA in the genetic maps presented later (see for example map 2).

The main visible aspect of the function of DNA is the form we take as a developing foetus, our general shape and what type of creature we are. However in many parts of our body throughout our life DNA continually reproduces itself. This replaces our worn out tissue. But mistakes do occur and cancers can result.

In fact mistakes in the sequence of nucleotides in the DNA are reasonably common and are called mutations. Even identical twins have a few dozen differences in their total DNA (Cavalli-Sforza 1995). Harmless mutations in your reproductive cells are passed on to your descendants. These mutations lead to variation in the genetic makeup of individuals, and ultimately of different populations. In some cases it has been possible to work out the sequence in which such mutations have occurred. We’ll come back to this soon.

Apart from reproductive (sperm and egg) cells each cell of the human body has 46 chromosomes, made up of 23 pairs. Chromosome pair 23 is either a pair of X-chromosomes or a single X and a single Y chromosome. This determines whether you are female (XX) or male (XY). This is not true for all creatures. In birds and butterflies for example it is the female that has the equivalent of the XY combination.

Reproductive cells have only one of each pair of each chromosome, i.e. for humans 23 chromosomes including either a single X or a single Y. When fertilization occurs the normal condition of pairs is restored, one of each pair from each parent. Individual chromosomes are not passed unaltered from generation to generation though. Pieces can cross between the pairs of chromosomes during the formation of the reproductive cells. Because of this, genes from each parent can be thought of as mixing sort of randomly for the next generation. Gene linkages do occur, basically because genes close together on the chromosome are less likely to be separated (Jobling et al 2004). For example the genes for blond hair and blue eyes usually go together in humans, although they do show some independence.

During the formation of reproductive cells the pair of X-chromosomes in women behaves in much the same way as all the other pairs of chromosomes do, they mix. But, because there is no corresponding part on the X-chromosome for it to join with, most of the Y-chromosome is passed virtually unchanged from father to son. And virtually all genes on the single X-chromosome in men, which can come only from their mother, are expressed. This is why such things as baldness in men come through the mother’s side. Scientists have worked out the sequence of nucleotides in sections of what is called the non-recombining portion of the Y-chromosome (NRY). The differences reveal how closely related male members of different populations are. Scientists have constructed a family tree for the human Y-chromosome (“MtEve” [The Trees]). Large sections of it came from such witnesses for the defence as Hammer and Horai (1995), Karafet et al (1999), Underhill et al (2001) and Ke et al (2001). We are getting to know a great deal about migration of at least the male half of the human population. But we cannot automatically assume these movements always indicate population migrations that included women. It is not only married men who migrate to new regions. Any man who travels a lot can spread his genes, including his Y-chromosome, quite widely. For many reasons women’s genes usually spread more slowly.

Nuclear DNA

DNA is ultimately responsible (via RNA) for making proteins. Living matter is made up largely of protein. Matt Ridley (2000) writes “almost everything in the body, from hair to hormones, is either made of proteins or made by them”. Proteins are just long chains of amino acids. Twenty amino acids are commonly found in nature. Each amino acid is, in effect, coded for by a particular sequence of three nucleotides on the DNA. The pattern of nucleotides on the DNA therefore ensures a particular protein always has the same sequence of amino acids; but any mutation in the DNA can change some aspect of the protein it is responsible for and even the creature itself. It has been shown statistically most mutations seem not to have any effect though (Lewin 1999).

Any harmful protein change would usually be eliminated during foetal development, or possibly even before conception. Mutations that provide an advantage for any individual with it are probably very few and far between. Harmless protein changes move slowly through a population, as individuals with the mutation move around and leave descendants. But particular mutations are usually concentrated in particular geographical regions. The book “History and Geography of Human Genes” by Cavalli-Sforza et al (1994) can provide many hours of contemplation. It contains about 500 maps of the distribution through the world of various genetically controlled blood proteins and enzymes. Further processing of this data by a system called “principal component analysis” has provided maps of mutations that tend to occur together in clumps. The map of the first principal component for each region shows the distribution of the greatest level of genetic variation within that region.

Because, by definition, the maps pick up only genes that display regional variation the two opposite extremes are usually each concentrated in separate regions, but they merge gradually into each other. Once the regional genetic combination that makes up the first principal component is removed the next most common one (second principal component) is revealed, often showing a completely different pattern, and so on.

Studying these maps gives us an indication of the migration of different human populations around the world and the defence will call on Cavalli-Sforza’s maps many times as evidence in favour of the defendant. Of course humans, like all species, share the vast majority of their genes with each other. That is why we all look roughly the same but this case will concentrate mainly on those genes that vary within each species and group of species.

Although DNA evidence is readily accepted in Courts of Law to establish close relationships or the identity of individuals it does seem as though many of us are unwilling to accept DNA evidence of relationships in the present case. Of course the same mutation at the same point on the DNA molecule in two different individuals at different times may lead to our misinterpretation of the evidence in some cases.

So at conception you received genes from each parent in the ratio of 50:50. Some research suggests that the egg is able to select the best sperm, but the selection of genes from each parent is basically random. So when you were conceived you took half your genes from your father and half from your mother which, mixed together, make up your characteristics.

Dominant and Recessive Genes

Each of your genes provides two possibilities, one from your mother and one from your father. Any gene always expressed as a characteristic is called the dominant gene. By convention the dominant gene is written with a capital letter, e.g. “B”. The lower case letter, “b”, is used for the recessive (the one that usually doesn’t show). Because each individual has two genes for each characteristic the only possible combinations are “BB”, “Bb”, “bB” and “bb”. You can put the gene from your mother or your father first but be consistent. It sometimes makes a difference whether the gene comes from the mother or the father (Jones 2000). The reasons for this are complex and needn’t concern us. “BB” and “bb” are called “homozygous” (the same gene on each chromosome) and “Bb” and “bB” are called “heterozygous” (different gene on each chromosome).

Dominance can actually be complete or incomplete. In the case of complete dominance the first three examples above would all look the same for that characteristic. Just the one individual in four with the combination “bb” would look different. In cattle the black colour is dominant. In that case “B” could represent a dominant gene for the colour black and “b” represent a recessive gene for the colour white. The combination “bb” would be the only one that would produce a white animal. The other combinations would all be black.

A particular gene always occurs at a particular section of a chromosome. In each individual only two options are available because they have pairs of chromosomes, one of each pair from each parent. But in the population as a whole there may be many different genes available for that place. Human blood groups, for example, have three options on the chromosome: A, B and O.

Four blood groups exist: O, A, B or AB. O is recessive and so always homozygous (oo) but A and B can be homozygous (AA and BB) or heterozygous with O (Ao and Bo). AB is an example of incomplete dominance. This is what makes us all so different. And in the case of the B and b example a gene for a reddish-brown colour could be available as well as genes for black or white. This complicates things but dominance may still be complete. Black may be dominant over both red and white, and red dominant over white for example.

Some genes are co-dominant or cumulative: the heterozygous “Bb” or “bB” can be sort of halfway between the homozygous “BB” and “bb”. For the example of black and white given above the heterozygous individuals would be some shade of grey. With the addition of the red gene a combination of red and black could give a dark brown or bay colour, and red and white a fawn or dun colour. In some cases heterozygous individuals (“Bb” or “bB”) are actually at an advantage over either homozygous extreme. This is one of the things that ensure “hybrid vigour” or “heterosis”. In practice, though, characteristics that vary along a continuum between two extremes are usually the product of several different pairs of genes at different places even on different chromosomes, which individually demonstrate complete dominance.

In actual fact black is not the dominant colour in all animals. For example white is dominant in cats. In this particular case the gene that gives rise to the white also leads to deafness and white cats, especially males, are usually deaf (Jones 2000). This means there has been what is called “selection” against white cats, otherwise all cats would be white (I would bet there has also been selection against white cats for other reasons as well. Except in snow a white cat is easier to see when it is hunting or being hunted for instance).

The concept of selection has been borrowed from farming. Farmers control which individuals in their dairy herd, for example, will be able to leave more genes in the form of descendants. They do this by “selecting” which animals to either breed from or get rid of. In effect nature does much the same thing with animals and plants. If individuals with a particular characteristic are less successful at breeding those without the characteristic will make up the population numbers. This is called natural selection.

Selection keeps disadvantageous mutations at a low level. But if a dominant gene appears in a population it obviously spreads very rapidly through the generations if individuals with it leave more offspring that in turn leave more offspring etc. A recessive gene spreads more slowly because selection can operate only on individuals where the gene is expressed, i.e. those born with a double recessive. If individuals with a double recessive leave more offspring after many generations the whole population will have become double recessive. The dominant gene will then be extinct. By that time another advantageous recessive may have arisen in the population at the same point on the chromosome. In this way a recessive gene can become dominant but not, of course, over any gene it had previously been recessive to. The defence will expand on this in “Hybrid vigour and Inbreeding” [Wave Theory of Evolution].

And I’m afraid it is not really even that simple. Many animals have genes that make the two colours paler, appear in patches, stripes or spots on their bodies, and some even have three colours. Calico, or tortoiseshell, cats for example can have three colours. Most genes for colour in cats happen to be carried on the X-chromosome. To get a tortoiseshell and white cat there has to be a red gene on one X-chromosome and a black gene on the other X-chromosome as well as other genes that promote patching with white. Because males have only one X-chromosome tortoiseshell cats are usually female. Any males that are tortoiseshell-coloured must have an extra X-chromosome and they are sterile.

Genetic information therefore is carried in a way that allows an almost infinite variety of possibilities. A number of genes are available for each point on the chromosome and a number of points on the chromosome can carry similar genes. There are also genes responsible for switching on or off other genes. In fact most characteristics are almost certainly the result of a series of such genes (Ridley 2000). For any characteristic there is a sort of hierarchy of genes. Whether a gene is dominant or incompletely dominant is probably also ultimately under genetic control.

For practical purposes we can regard populations, or whole species, as being simply collections of genes, or nuclear DNA, in various proportions. The study of this is called population genetics and the defence will use information gained from studying cattle to explain the idea many times during this case. Because a great deal of information is available for cattle they are ideal for the study of practical genetics. Not only have desirable qualities been bred for; the change each generation can actually be measured.

Meat quality, weight and growth rates for beef cattle progeny can be measured accurately. In dairy cows milk production, protein and fat percentage in the milk, overall size, temperament, teat placement and udder shape are all to some extent genetically controlled and can be measured, or at least subjectively judged. All these individual traits have what is called a bell curve distribution. As you move away from the most common type in any direction numbers fall off in the shape of a bell. The further from the majority you get the fewer individuals there are. The jury will eventually understand how we can see that in effect each individual gene travels through a population on its own independent wave.

My grandfather milked Shorthorn and Red Devon cattle breeds. By the time my uncles took over the farm Jersey cattle had become the fashion. But they didn’t need to buy a whole new herd. They just formed a sequence of hybrids with Jersey bulls. After three cow generations the herd was ⅞ Jersey (“Pedigrees” [Ancestry]). They looked like Jerseys but when I was a child some cattle in the herd still had pink noses or were brindled, a throwback to the earlier breeds. Their fathers had Shorthorn or Red Devon ancestry too.

When Friesian cattle then became popular it was again possible to gain a Friesian herd by the same method. But the mitochondrial DNA of many Friesian cows in the New Zealand dairy herd goes right back to Shorthorn or Red Devon cattle.

Mitochondrial DNA

So far we have been dealing with nuclear DNA, the DNA responsible for your genes. But there is another type of DNA in your body. It is called mitochondrial DNA (mtDNA). This DNA is not involved with the formation of genes (Jones 2001) and it occurs as a circular molecule (the ends are connected). Human mitochondria each consist of just sixteen and a half thousand pairs of the nucleotides: A, T, G and C. Each cell of the human body may have up to ten thousand molecules of mtDNA but most have far fewer. Mitochondria occur outside the nucleus and are known as the powerhouse of the cell.

They produce the proteins responsible for digestion within the cell. These proteins are involved in the production of ATP (adenosinetriphosphate) from various acids produced in the body. This process takes up oxygen and produces carbon dioxide and water. In the vast majority of individuals all the mitochondria in every cell have exactly the same DNA but mutations do occur. If the mutation happens in an egg cell it is passed on to the offspring.

The egg cell needs its mitochondria for metabolism and cell division but the sperm’s mtDNA is effectively discarded and lost at fertilization (Jobling et al 2004). Therefore the mtDNA is passed unchanged from only the mother to the child for thousands of generations. In fact the mtDNA does change over time (mutations). The rate of this change and the regularity of the change have been greatly debated by scientists; i.e. does it have a sort of half-life? How much does it change, say, in a thousand years? Is the change totally random or does selection act on these changes? It is now generally accepted that some sections of mtDNA change quite rapidly and regularly, and it has been shown that one parent-child comparison in forty has a mitochondrial mutation (Jones 2000). Because there is a great deal of mtDNA in each individual, and it is a relatively short chain, it has been the easiest DNA to extract and to study.

Like the Y-chromosome, the sequence of the nucleotides in sections of the mtDNA has been worked out for individuals of many species. The accumulation of differences in the sequences can be used to indicate the relationship of various groups of animals and humans through their mother’s ancestry. If the mtDNA is only a little different it is presumed they are closely related and of course this would be so, no matter what the rate of mutation.

Again, like the Y-chromosome, examination of the mutations in human mtDNA has been used to construct an evolutionary, or family, tree. From this it has been concluded we all descend from a single woman who lived in Africa. We will meet her again and see her family tree in “MtEve” [The Trees]. But before then the defenve needs to explain a few more things.

Studies of the changes in mitochondrial DNA and the Y-chromosome have been very useful in helping us understand our origin but we need to consider other evidence before we jump to conclusions. The first thing we need to consider, and explain, is the present distribution of human genetic variations.

Witnesses Called

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

Cavalli-Sforza, Luigi Luca and Cavalli-Sforza, Francesco (1995) The Great Human Diasporas. Addison- Wesley

Hammer, Michael F. and Horai, Satoshi (1995) Y Chromosomal DNA Variation and the Peopling of Japan. Am. J. Hum. Genet. 56: 951-962

Jobling et al (2004) Human Evolutionary Genetics. Garland Science, New York.

Jones, Martin (2001) The Molecule Hunt. The Penguin Press, London.

Jones, Steve (2000) Almost Like a Whale. Anchor, London.

Karafet et al (1999) Ancestral Asian Source(s) of New World Y-chromosome Founder Haplotypes. Am. J. Hum. Genet. 64: 817-831.

Ke et al (2001) African Origin of Modern Humans in East Asia. Science Vol. 292 1151-1152

Lewin, Roger (1999) Patterns in Evolution. Scientific American Library, New York.

Ridley, Matt (2000) Genome. Harper Collins, New York.

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

Underhill et al (2001) Y-Chromosome Haplotypes and Implications for Human History in the Pacific. (pdf) Human Mutation 17: 271-280.

Human Evolution on Trial - 'Time' - by Terry Toohill

Human Evolution on Trial - 'Time'

History needs dates and so the defence had better provide a framework for all this evidence. To understand the lengths of time involved for various events during the earth’s history try this summary. It is an exponential time scale. There is a condensed version in the form of a chart starting a few pages ahead and you will be able to refer back to it when necessary during the rest of the trial. But first of all I’ll explain it.

The most recent events are at the top, or beginning of the chart, as they are in geological strata or layers. The older, or lower, layers are compressed, also as they are in geological strata. To read it in the order things happened you have to start at the bottom, or at the end of the chart, (p.88) but you can start anywhere. As you move back in time, or down the list, each division covers the same length of time as everything before it (or above it). As you move up the column towards the present each division halves the time between then and today. The chart has the advantage of being close to how we actually view time because as Gohau (1991) writes “every history favors the present over the past, if only because of the unequal amount of data available for the two”. I have juggled the figures a little in places to produce more significant dates but it still basically doubles all the way.

To make it relevant for humans I will start with a human generation of twenty-five years and keep doubling the time. For convenience we’ll begin at the year 2000 AD. Twenty-five years takes us back to 1975. Fifty years ago it was 1950, soon after the end of the Second World War. Double it again and we are back 100 years, the beginning of the twentieth century.

Doubled yet again takes us back to 1800 AD when we each have over two hundred and fifty ancestors in our “Pedigree” [Ancestry]. The steam engine had just come into general use (Fyrth and Goldsmith 1965) and so we could use this date to mark the beginning of the Industrial Revolution and the beginning of geology.

Double again to four hundred years ago and we are about the time of the death of Queen Elizabeth I of England (March 1603). We are well into the time of European exploration, exploitation and expansion around the world and the beginning of the latest round of extinctions. We are nearing the time of a million ancestors each. The invention of both the telescope and the microscope around this time meant science could begin. Both Lucilio Vanini and Giordano Bruno were burnt at the stake for their beliefs. Archbishop Ussher calculated the earth had been created in 4004 BC, near enough to 6400 years ago.

Eight hundred years takes us back to just 1200 AD though. You saw in “Change” [Destruction] there is no doubt Maori were well established in New Zealand by this time. The Crusades were well under way and Genghis Khan took control of the Mongols.

Sixteen hundred years ago marks the withdrawal of the Roman Empire from much of Western Europe, although an argument can be made that “The West” is a continuation of it. The Anglo-Saxon movement into England coincided with its temporary disruption in Britain. Human expansion beyond Samoa into Eastern Polynesia was well underway.

Double 1600 years to 3200 years ago (1200 BC) and people using Lapita pottery were about to reach Tonga and Samoa (“Pacific Population” [Lapita]). We are also at about the time of Ramesses III of Egypt and the migration of the Sea People through the Mediterranean Islands, “The Last Point” of the human star. It may also be the time of any kingdom of Israel in the Middle East under David and Solomon although not all people regard all these events as being contemporary. I’ll return to this in “Culture” [Evolution of a Religion].

Double again to 6400 years ago (4400 BC) and we are at about the beginning of cities in the Tigris and Euphrates River valleys (Mesopotamia) in what is now Iraq. Much older towns have been found just outside the region though (for example at Jericho). Record-keeping through the use of writing probably began around this time. And Archbishop Ussher believed the earth had been created then. Balkan people were working copper (James 1991) and the Austronesian-speaking people began their expansion from Taiwan (“Polynesian Origins”). People with the Linear Pottery or Danubian culture were moving into Europe.

If we double again we reach 12,800 years ago but we’ll round the date to 12,500. We are near the end of the ice age and the beginning of human movement into the extreme end of the Northwest European point of the human star and into the American sub-point. The first steps towards farming were probably also made at this time both in the Middle East (the Fertile Crescent) and in Southeast Asia (the Hoabinhian culture).

Double the time again and we have 25,000 years ago, about the time people with the “Gravettian” stone-age culture moved into Western Europe from east of the Carpathian Mountains, from Southern Russia. Modern humans finally replaced the Neanderthals, probably at least partly through the formation of hybrids (“Neanderthals et al” [Aurignacian and Mousterian]). The Gravettian people probably used the same route the Corded Ware people were to take 18,000 years later (see “Indo-Europeans” [Mingling]). The jury will meet the Gravettian again several times, especially in Part V. African and European cattle separated at about this time.

About 50,000 years ago humans known as Cro-Magnon started moving into Europe, most likely from the southeast via Turkey and Greece (“Out of Africa” [Cro-Magnon]). They introduced the “Aurignacian” technology. At the opposite side of the human star people were able to move “Into Australia” for the first time.

Fully modern humans (Homo sapiens) are said to have left Africa by the time we double again to 100,000 years ago. They seem to have been held up in the Middle East because Neanderthals (Homo neanderthalensis) keep popping up there over this 50,000 years. We’ll return to the period from here to the present in Part V. In the meantime we’ll keep going back.

200,000 years ago we have Homo heidelbergensis in Europe (the first fossils of it were found near Heidelberg). Neanderthals and modern humans both presumably developed from this species (possibly with some input from earlier Homo erectus). Neanderthals’ culture is called “Mousterian” and involved the “Levallois” technique of working stone.

The Levallois developed some time between 200,000 and 400,000 thousand years ago and 400,000 years ago is about when Homo heidelbergensis developed, presumably from some sort of Homo erectus. The defence will present evidence from this period in Part IV (“Technology” and “Species or Not”). We’ll return to this summary of “Time” over the page but now is a convenient place for us to have a rest and for me to show you the chart.

A Short History of the Earth

Years ago Significant Event

0. 2000 AD The New Millennium

25 One generation, back to 1975. I left the Manawatu and returned to Northland

50 End of Second World War (roughly). I was born (a little less roughly)

100 Beginning of the twentieth century. Humans found they could fly after all

200. The Industrial Revolution began and Europeans started moving into Australia and New Zealand

400. Time of Queen Elizabeth I. Europeans off learning about the world.
     

800. Maori in New Zealand by this time. Inquisition established

1600. Decline of Roman Empire, Anglo-Saxons into England

3200. About the time of Ramesses III of Egypt and the Kingdom of Israel. Lapita pottery people to Tonga and Samoa

6400. Cities developing in the Middle East and possibly Egypt. Linear pottery-bearing and Austronesian-speaking people begin their expansion

12,500 End of ice age. Beginning of farming and Hoabinhian culture. Humans able to enter what I call the American subpoint of the human star

25,000 In Europe the Gravettian stone tool culture moved in from the northeast

50,000 Aurignacian stone tool culture into Europe from the southeast. (Cro-Magnon man). First humans into Australia

100,000 Human expansion out of Africa. They and Neanderthals alternate in the Middle East for half the time between today and then.

200,000 Mousterian (Neanderthal) stone culture and evidence of controlled use of fire in Europe.

400,000 Evolution of Heidelberg Man and Levallois stone working.

800,000 Homo erectus reaches maximum distribution around the Earth.

1.875 million Evolution of Homo erectus in Africa and Asia. Ice ages well established.

3.75 million Good fossil evidence for Australopithecus (Lucy).

7.5 million Roughly time of split between humans, chimps and gorillas. Three-toed horses out of America.

15 million Africa became jammed into Asia and Europe. Ancestors of modern apes able to move between these continents.

30 million Mid-Oligocene geological epoch. Apes separated from monkeys during this period.

65 million End of the Cretaceous geological period and the dinosaurs. Continents started splitting and age of mammals began. Monkeys already developing.

130 million Beginning of Cretaceous (end of the Jurassic period). The Cretaceous fills half the time between today and then.

260 million Beginning of the Permian geological period. Most of the oldest rocks in New Zealand were laid down over the period from the Permian to the end of the Jurassic. Again this took up half the time between today and then

520 million End of the Cambrian geological period. The first mass extinctions we are aware of.

1040 million Possibly an ice age.

2080 million So long ago I can’t remember what happened here.

4160 million Round about the beginning of the Earth.

Now to carry on:

As I said by 800,000 years ago the species Homo erectus had probably reached the geographical extremes of their range. You saw it was not until four divisions more recently that humans were able to expand further, “Into Australia”.

Double again to 1.6 million years ago and we have Homo erectus beginning their expansion. “First Humans” will be about these people. The latest series of ice ages had started a little before this time. There have been up to twenty cycles of extreme cold followed by periods as warm as or warmer than today. The climate had actually already been steadily cooling for more than 30 million years before this though. The period of the ice ages is known as the “Pleistocene geological epoch”. The beginning of the Pleistocene, about two million years ago, also marks the end of the Tertiary and the beginning of the Quaternary geological period.

Homo erectus evolved more than 1.7 million years ago but I’ll use 1.875 million years. When that is doubled it comes up 3.75 million years ago. From about this date there is good fossil evidence in “The First Point” for presumed Homo erectus and human ancestors, in the form of “Lucy” and other Australopithecus species (Johanson and Edey 1982). Some genetic evidence has been interpreted as showing humans, chimpanzees and gorillas may have finally separated as recently as this date (Gribbin and Cherfas 2001). Various species of Equus and camels moved out of North America also about this time.

Doubled again is 7.5 million years and three-toed horses moved out of North America. This is also about the earliest time given for the split between chimpanzees and humans, although gorillas may have separated even earlier. A fossil of this age that could well lie on the line to humans has recently been found just outside “The First Point”, in Chad (Lemonick and Dorfman 2002). I’ll return to the evidence for the evolution of various human types, and their technology and culture, in Parts IV and V but I am on a roll and for now I’ll just keep doubling the time until we arrive at the beginning of the earth.

Fifteen million years ago, in the middle of the Miocene geological epoch, Africa became jammed up against Asia and Europe (Attenborough 1987). This allowed the ancestors of the modern (or brachiating) apes to move between Africa and Asia (brachiating is the ability to swing or hang from branches by your arms). In fact it’s possible the ancestors of the present African apes (including humans) actually moved into Africa from Asia (Gribbin and Cherfas 2001). The gibbons may have separated from the rest of the ape line as early as fifteen million years ago. They have become particularly effective brachiators. The orangutan separated eight to ten million years ago.

Double again and we are in the middle of the Oligocene geological epoch, at 30 million years ago. Three-toed horses appeared in North America and the ancestors of deer and giraffes separated from other ruminants during this period. Camels and llamas had already parted from them. The defence will use evidence from these and many other species to prove the wave theory in the remainder of Part III. Apes may have separated from monkeys during this period. Apes diverged into many species most of which (apart from some of the later brachiating ones) eventually became extinct.

During the Oligocene the continents were at their lowest altitude, having been eroded down since well back in the Cretaceous period. The climate was very warm and seas were at their highest. From the Oligocene until the present the continents start bumping into each other again. Mountains rise and the sea is able to sink into deeper ocean basins. This period also marks the beginning of the climate cooling that led ultimately to the latest series of ice ages. The immediate cause of the cooling was probably the opening of the gap between Australia and Antarctica. This allowed the southern circum-polar current to develop (Stevens 1985).

Double again and we have 60 million years but we’ll make it 65 million years, which marks the end of the Cretaceous geological period and the beginning of the Tertiary geological period. It also marks the extinction of the dinosaurs and beginning of the age of mammals. Some people believe the dinosaurs didn’t actually become extinct. Small versions that had evolved feathers, probably to keep warm, evolved into birds.

The Cretaceous itself in fact lasted about 65 million years and so the Cretaceous began 130 million years ago. This earlier date marks the end of the Jurassic period and the beginning of another breakup of continents. Virtually all the sea floor on earth is younger than this date and most of it is younger than half this age (Jones 2000). The lowering of mountain ranges by erosion and the gradual filling of sea floor with the sediment during the sixty-five million years of the Cretaceous eventually had the effect of raising sea levels and partially flooding the continents.

The gradual isolation and size reduction of the continents during the Cretaceous period and consequent climate and environmental change may have had as much to do with the eventual extinction of the dinosaurs outside North America as did the asteroid collision. Dinosaur extinction was actually very protracted; at least hundreds of thousands of years (Jones 2000). And possibly millions but humans like the idea of catastrophes. In fact many people hope the world is going to end soon.

The massive eruption of volcanoes on the Deccan plateau of India near the end of the Cretaceous would have contributed to the dinosaur extinction and could be partly responsible for the layer of heavy metals found in sediments from 65 million years ago throughout the world. Although Richard Corfield (2001) does mention this possibility he seems to suggest the idea has been rejected largely because of political and funding considerations. He actually offers no evidence to dispute it. Most mass extinctions have coincided with large volcanic eruptions though (Wade 2001).

The ancestors of monkeys and lemurs had separated from other mammals at some time during the Cretaceous, probably along with the development of flowering plants, especially trees (Tudge 1996). Flowering plants appeared in the mid-Cretaceous and the evolution of grass may have been the final straw, so to speak, for the dinosaurs. Grasses didn’t actually reach their major expansion until more recently though (at the beginning of the Miocene epoch about 25 million years ago) and ruminants or cud-chewing animals seem to have started developing a little before that time (“Evolution” [Ruminants]). The expansion of grassland was also responsible for the development of horses.

Double the time again and we get 260 million, the beginning of the Permian period. The Permian is actually in the Paleozoic geological era but the Paleozoic ends with the end of the Permian, about 235 million years ago. Great volcanic eruptions and a series of ice ages similar to the ones the earth has just been through mark the end of the Permian. But the continents were in much different positions than they are today. The time also marks easily the greatest mass extinction event we are aware of. It makes the extinction event at the end of the Cretaceous (which included the extinction of the dinosaurs) look relatively minor, about number five on a list of severity.

Double again: 520 million is the end of the Cambrian period, marked by the extinction of much of the variety of life that had developed by that time. The Cambrian began about 570 million years ago with a huge explosion of life forms (Corfield 2001). Supporters of the Intelligent Design theory of evolution apparently believe this happened through a creation (Wells 2000, and Dembski and Kushiner 2001). Anyway whether it happened by creation or not is irrelevant to this case although arguments both for and against will no doubt be presented when “The origin of Life” comes to trial. I’m sure the wave theory will be able to help us interpret the evidence. Besides, do we need to go even this far back if we are concerned just with Human Evolution from apes until today? This could become an incredibly long story. But I’ve nearly reached the beginning.

1040 million years is in the Precambrian era and someone else can look for significance in that date but some evidence suggests complex life began about then (Wade 2001). Intelligent Design supporters presumably would say through another creation event. Until James Hutton’s time most geologists used the idea that there had been several “creations” to explain the fact that throughout the world rocks of the same age have similar collections of fossils, many of them not present in more recent levels (Gohau 1991 and see “Long Ago” [Geology]). Most early geologists believed each group of earlier life had been destroyed by catastrophes. There had been a series of beginnings. Others began to see a basic thread that indicated life had changed or evolved through the history of the earth.

We can see that the same old argument carries on in the conflict between creationists and evolutionists. The term creationist covers a huge variety of beliefs though. Some of them even accept evolution has occurred but that it has happened by design (Wells 2000, and Dembski and Kushiner 2001).

The preference of any individual to accept either gradual or sudden change (or even no change at all) as an explanation for the development of life on earth depends very much on what has been, or is, important in their own life. It’s difficult for us to imagine the world has ever changed more than it has over our own lifetime. We also carry many mythconceptions from our childhood. I believe the conflict between a belief in gradual or sudden change is at the core of the debate between the “spread origin” and “single origin” theories of human development (see “Conception”). You will be able to decide for yourself which is the most likely theory after examining the rest of the evidence.

2080 million years may be significant (perhaps the beginning of life itself) and the earth is said to have begun a little more than 4160 million years ago.

Witnesses Called

Attenborough, David (1987) The First Eden. Guild, London.

Corfield, Richard (2001) Architects of Eternity. Headline Book Publishing, London.

Dembski, William and Kushiner, James (2001) Signs of Intelligence. Brazos Press, USA.

Fyrth, H. J. and Goldsmith, M. (1965) Science History and Technology Book 1. Cassell, London.

Gohau, Gabriel (1991) A History of Geology. Rutgers University Press, New Brunswick, USA.

Gribbin, John and Cherfas, Jeremy (2001) The First Chimpanzee. Penguin Books, England

James, Peter (1991) Centuries of Darkness. Jonathan Cape, London.

Johanson, Donald and Edey, Maitland (1982) Lucy. Warner Books, New York.

Jones, Steve (2000) Almost Like a Whale. Anchor, London.

Lemonick, Michael and Dorfman, Andrea (2002) Father of us All? Time, July 22^nd.

Stevens, Graeme (1985) Lands in Collision. Science Information Publishing Centre,

Wellington.

Tudge, Colin (1996) The Time Before History. Scribner, New York.

Wade, Nicholas ed. (2001) The New York Times Book of Fossils and Evolution. The Lyon Press, New York.

Wells, Jonathan (2000) Icons of Evolution. Regnery Publishing, USA.

Human Evolution On Trial - Eastern Polynesia - by Terry Toohill

Eastern Polynesia

The New Zealand Maori language is classified as part of the Eastern Polynesian group. Eastern Polynesian languages are spoken on most islands across the central Pacific, from Hawai‘i in the north, Easter Island in the southeast to New Zealand in the southwest (map 3). All the languages within the triangle are quite closely related and have probably diversified only in the last 1500 years or so. The defence claims we can use the Polynesians’ expansion into this previously uninhabited region of the earth to explain several ancient examples of human migration, and our evolution.

The Polynesian group, as a whole, includes Western Polynesian: Tongan, Samoan and some other related languages, both nearby and far to the west. The Far Western Polynesian languages are called the “Polynesian Outliers”. These are generally accepted as the product of movement west from the central Pacific. The Polynesian Outliers are scattered through parts of Eastern Melanesia: New Caledonia, Vanuatu and the Southern Solomon Islands. Most of the Melanesian languages are not Polynesian although many are related to it. We’ll come back to this next in “Polynesian Origins” [Language Families].

Fiji lies on the boundary between Polynesia and Melanesia. Some linguists consider the Fijian languages to be the closest to ancestral, or proto, Polynesian (Jennings 1979). We’ll come back to how the Polynesians’ ancestors reached Fiji in “Pacific Population” [Lapita]. It is difficult to know whether Samoa or Tonga were the first islands settled after Fiji. Both groups share with Fiji quite a common cultural heritage, and quite a movement from Tonga back to Fiji occurred even in historic times (Howe 1984). In Polynesian languages “Tonga” means “south”, “Tokelau” (tokerau in Maori) means “north”, “Tongareva” (rewa) may mean “float south”, “Tahiti” (tawhiti) means “distant” and “Tuamotu” may mean “islands beyond”. The defence suggests these names are significant for the study of Eastern Polynesia’s settlement.

Polynesian Languages

Comparison of language relationships, cultural variation and physical similarities produce the following diagram (Houghton 1980, and Jennings 1979). The dotted lines enclose the cultural groupings within Polynesia. Apart from New Zealand and the Chatham Islands, which are actually south of Fiji, the islands are in about their geographic positions (see map 3). The names by which the cultural groups are known appear in Italics and are underlined. The solid lines show language connections, the numbers the presumed place of development of language types.

Polynesian Evolutionary Tree.

The place of branching for 1, 2, 3 and 4 is fairly obviously in the stretch of islands between Tonga and Tokelau: South and North. Interestingly the island of Western Samoa is actually called Savai‘i, the same word in their dialect as the Maori place of origin: Hawaiki. Some of the languages spoken through the Northern Cook Islands, part of the Intermediate region, may branch off in the gap between proto-Nuclear Polynesian and proto-Central East Polynesian (Jennings 1979), which makes sense.

The earliest adzes in the Marquesas Islands resemble ones of the same age (about 2000 years) on Samoa (Bellwood 1978) and so it is generally accepted the people of Eastern Polynesia came from near Samoa. But the order in which the islands were settled and the place of development of the distinctive Eastern Polynesian culture are disputed. There are difficulties in accepting as candidates for the development of this culture any of the relatively large islands such as Hawai‘i, the Marquesas Islands, or Tahiti in the Society Islands.

A dispersal centre for Eastern Polynesians at 5 would eliminate all the contradictions (such as unexplainable patterns of change in culture and fishhook styles) introduced by placing it at any island group actually named in the diagram. Number 5 covers the islands of Tongareva, Rakahanga, Manihiki, Pukapuka and the Phoenix and Line Islands. Many of these small islands were uninhabited when Europeans first reached them but most showed signs of having been inhabited at some time. None are large enough on their own to be a centre for the development of Polynesian culture. But I would like to suggest each single coral atoll could have supported a large population for two or three generations, by which time another island would have been discovered and off they would all go again. I understand dog remains have been found in the Northern Cook Islands dated to about the right time to support the idea of this migration route.

Islands

McGlone et al (in Sutton 1994) call finding previously unoccupied islands the prehistoric equivalent of winning a lottery. With huge populations of birds and animals with no fear of humans, and undisturbed fish and shellfish in the surrounding sea, there would have been no shortage of food for these first arrivals. The huge populations of foraging seabirds would also have made unoccupied islands effectively bigger targets and easier to find than they would be today. Any volcanic islands would be sources of stone for tools, implying a great deal of deliberate two way voyaging. The whole process provides easily enough time for the culture to diverge from Samoan and become recognisably different and diversified by the time the Marquesas, Society (Tahiti) and Hawai‘ian islands were settled. In Part IV the defence will suggest that several early human expansions through open grassland containing scattered clumps of trees were similar.

The defence will later show that the pattern of animal “Extinctions” [What Have We Done?] can be used to date human expansion. But the lack of evidence of extinctions in the Pacific islands, apart from New Zealand (“Change” [Destruction]), is more a result of a lack of research than that it didn’t happen. There is evidence of extinctions in New Caledonia, Hawai‘i and Fiji but these are the only islands where such study has been done. Even then only Hawai‘i and New Caledonia have been well studied and they show many extinctions occurring at the expected time. The Polynesian rat also gets to all the islands at the expected time with an apparently early date for New Zealand. People were just beginning to move beyond Western Polynesia at the time the rat appeared in New Zealand (some time between 300 BC and 300 AD). You saw in “Change” [Destruction] there is also evidence of man-induced fires in the eastern North Island this early (Elliot, Manighetti and Carter, 2003).

The ancestors of the Maori didn’t actually arrive in New Zealand and the Chatham Islands direct from the Northern Cook Islands, or the area of number 5. Of course my diagram is a bit simplified. There is quite a bit of evidence, such as the types of stone tools found in each region dating to the appropriate time, that the first settlers actually came to New Zealand mainly via the Southern Cook and Austral Islands (Sutton 1994). The recent arrival in New Zealand of people from Tonga and Samoa represents the opening of a new migration route. There is really no evidence any migration direct from that region contributed to the prehistoric population of New Zealand, but it is not impossible.

David Tuggle (Jennings 1979) postulates the settlement pattern for Hawai‘i was the same as that suggested by James Belich (1996) for New Zealand: a dispersal of people around the most easily exploitable regions at the first colonisation (“Change” [Destruction]). Population growth eventually pushed people into less desirable locations. This was probably the pattern on all the islands and certainly seems so on the Marquesas (Howe 1984). All human migrations into uninhabited regions, including very ancient ones (see “The First Point” [Homo habilis]), have probably been similar. The rapidly advancing wave lives off the easy pickings. People left behind, or coming in following waves, have to adjust to fewer resources. Sometimes those left behind have even become extinct and disappeared entirely.

I believe it may have been during the first stage of movement into the Pacific Ocean beyond Western Polynesia that the legends of the hero Maui fishing up islands (discovering them?) developed. More islands kept appearing ahead of the migration wave and, by human assumptions or Chinese drover’s clever dog syndrome, someone must have made them or brought them up. It was handy if, in the future, you could claim your ancestors had been on the island when Maui fished it up though.

Study of the distribution of Polynesian myths could be revealing. For example it would be interesting to know if the name Kupe is confined to New Zealand. We do know the islands of the Marquesas and Mangareva have a similar hero named Tupa (Orbell quoted by McGlone et al in Sutton 1994). Therefore Kupe is possibly a general name for an explorer; in other words any great sailor was given the name “Kupe.” So Kupe could represent a string of people given the same name because they had the same attributes, as probably does Maui. The defence will suggest some other examples from oral tradition in “Culture” [Evolution of a Religion].

Marginal Polynesia

Loss of genetic variation during their evolution means Polynesians from the many different islands are remarkably similar to each other. I met native Hawai‘ians in a bar in Arkansas, USA. The Hawai‘ians looked exactly like New Zealand Maori. In fact when I first entered the bar I thought, for a while, I’d been magically transported to some bar in New Zealand.

The Polynesians are known as a large-framed people (Houghton 1980). This large frame is an unusual characteristic for both tropical and island populations. Generally speaking creatures in tropical regions tend to be smaller, or at least thinner, than are their relations in cooler areas. This is called “Bergmann’s rule” (Stringer and Gamble 1993). We saw in “Hybrid Vigour and Inbreeding” [Survival] it is also a general rule that creatures that are large on a mainland tend to be smaller on islands (Malcolm Browne in Wade 2001). The most likely explanation for the unexpected Polynesian physical type is that cold, wet nights, especially those spent at sea during migrations or fishing expeditions, would favour the survival of individuals with a larger body mass (Howe 2003). Smaller people lose heat much more rapidly and would suffer hypothermia. Movement between islands within Polynesia also offset the usual tendency for creatures on islands to become smaller. In other words the populations were not actually confined to single small islands. This would also help counter inbreeding.

Physical features of the people of each island group are closest to those of their nearest neighbours. This means there is basically a gradient of variation from the widespread islands of marginal Polynesia all the way back to Western Melanesia, a cline. Even where it is obvious there has been a movement back into Melanesia by Polynesian-speaking people originating from the area within the above diagram (Howe 1984) the cline is maintained. These people have now become genetically mixed with their neighbours (Melanesian people) but maintain their Polynesian language (the Polynesian Outliers).

But at the eastern end of the cline populations of the various widespread groups of islands are more similar to each other than they are to their nearest neighbours in the Central region. This doesn’t prove movement around the edge but suggests the lines in the diagram don’t represent single migrations. Kazumichi Katayama (Sutton 1994) shows that people from the Southern Cook Islands are as similar to Samoans as they are to New Zealanders. This indicates there were a series of genetic movements or waves along the old routes. In fact both genetic and linguistic evidence supports the idea of a series of movements along the lines.

Tracing changes in the languages shows the marginal area generally preserves older versions of the ancestral language but innovations in the Central area have spread unevenly into the marginal regions. In fact the innovations appear not to have reached Easter Island at all. That language preserved elements of Western Polynesian languages (Bahn and Flenley 1992). In “Indo-Europeans” [Celtic] you will see a similar thing happened with the Celtic languages. Ray Harlow in Sutton (1994) suggests regional dialects spoken in New Zealand may reflect changes in the dialects spoken in the Central islands. In other words there were several movements into New Zealand from several places but probably over a short period, say 200 years at most. During the remainder of this case the defence will present many examples of linguistic, genetic, technological and even religious innovations in a central area failing to reach the margins.

Easter Island

To finish this look at Eastern Polynesia we’ll take a quick look at the extreme eastern margin of their distribution, Easter Island. It provides excellent evidence for interpreting the whole pattern of human expansion around the world. But the jury will see the Polynesians are basically part of a cline stretching all the way to Indonesians, Filipinos and Malays.

Genetic evidence shows the first people on Easter Island were from Central East Polynesia (Lewin 1999) and physical appearance, language, culture and technology all support this. They arrived on an island reasonably well forested with Sophora trees (called kowhai in New Zealand), palms and several other kinds of tree. Archeology reveals the first settlers used the wood for canoes and dined magnificently on deep-sea fish, dolphins and turtles, as well as nesting seabirds. But by the time Europeans first saw the island no sizable trees remained and the people were no longer able to make canoes and to fish at sea (Bahn and Flenley 1992). The trees had been cleared for firewood and cultivation, and the rats Polynesians had brought with them prevented regeneration because they ate any seeds. The seabirds had also died out (Diamond 2005).

Increasing Population + Diminishing Resources = Strife + Selection

In myth the population had become divided into two warring groups: “Long Ears” and “Short Ears”. There is no evidence these groups had a separate origin other than possibly being a previous “upper class” and a “lower class” (Roberts 1989). The resulting strife, and selection, was not nice. The jury will see that, far from being the centre of a magnificent Pan-Pacific prehistoric culture as claimed by some people, they represented the last, doomed and impoverished remnant of a population movement that had come one third of the way round the earth after leaving Taiwan more than 5000 years before. The defence now needs to explain how we know they came from Taiwan.

Witnesses Called

Bahn, Paul and Flenley, John (1992) Easter Island, Earth Island. Thames and Hudson, London

Belich, James (1996) Making People. Penguin Press, Auckland.

Bellwood, Peter (1978) Man’s Conquest of the Pacific. Collins, Auckland.

Diamond, Jared (2005) Collapse. Penguin Books, London.

Elliot, M., Manighetti, B. and Carter, L. (2003) Dating the Human Colonisation of New Zealand. Proceedings of the New Zealand Geographical Society.

Houghton, Phillip (1980) The First New Zealanders. Hodder and Stroughton, Auckland.

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

Howe, K. R. (2003) The Quest for Origins. Penguin, New Zealand

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

Press, Canberra.

Lewin, Roger (1999) Patterns in Evolution. Scientific American Library, New York.

Roberts, Neil (1989) The Holocene. Basil Blackwell, Oxford.

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