Recently I wrote a piece kind of throwing together the ideas of human evolution and personal genealogy, two things that clearly are ultimately connected because they both come down to simple genetics and who begat whom, but in reality are so separated in time that we cannot properly connect them. But those who accept genealogies and DNA tests for paternity have to accept evolution, because the concepts are the same. Ultimately genes work a certain way and we understand how they work quite well. Evolution is no great mystery or controversy. What is amazing is that Darwin, with no concept of genes, came up with a system that once genes were studied was found to fit very well how genes actually work. Genetics and Evolution started as separate fields, but amazingly the two separate fields merged almost perfectly. To me genealogy is simply what we can see up close of our evolutionary path. Once we get a few generations back, the branches of our ancestry become quite tangled and hard to see...but they are there. And their imprint is in our genes.

Recenly some new developments occurred in studying human evolution that I now want to fit into my previous thoughts on the subject. Slowly it seems like the path of human physical and cultural evolution is being outlined, and I am enjoying each new piece of information.

I am fascinated by the development of humans first as a species, then into the variety of cultures, ethnicities, religions, etc that we are today. History, archaeology and biology all feed into this. I am by profession as biologist (currenly in Developmental Genetics, but previously mostly Cell and Molecular Biology), so evolution and how genes work is very familiar to me. I also love archaeology and history as a hobby. I spend a great deal of time reading and thinking about these subjects.

One issue I encounter is the idea that the study of human genetics and the evolution of humans as ethnically diverse opens the door to racism. I do not believe this is true even though I know that people who misunderstand or misuse the science can sometimes reach conclusions that are clearly racist. An extreme example of this was an early theory of human evolution that hypothesized that Africans were descended from gorillas, Europeans from chimpanzees, and Asians from Orangutans. This theory was based on almost nothing except racist beliefs. In the end science showed this was absurd and we moved on to realizing humans are merely, to borrow the term from Dr. Jared Diamond, a third species of Chimpanzees, closely related to the common chimp and the Bonobo.

I also remember the relatives of a woman I used to date challenged me with a very racist theory that generations of adverse conditions would mean that blacks had become inferior to whites. These people prided themselves on their intelligence, but they were ignoring two very basic ideas. First off, their concept of evolution sounded amazingly like the discredited theories of Lamarck who believed acquired characteristics were inheritied (something that MIGHT account for a small part of bacterial evolution, but not any other evolution). And second, they ignored the fact that adverse conditions often mean a greater selective pressure, quite possibly selecting for intelligence, strength, whatever it took to increase survival. Trying to bend the concepts of genetics and evolution to fit a racist idea of superiority will not work because this is not how evolution or genetics works.

One of the difficulties in all of this is that when genetic differences are found between different groups of people, too often people think of it in terms of "superior" and "inferior," or "normal" and "abnormal." But genetics doesn't work like that. A healthy species is a genetically diverse species and any concept of a "master race" is not only unfounded based on the clear genetic mixing of human populations, but is actually undesirable. Another term for "master race" would be inbred. Genetic diversity is pretty much ALWAYS a good thing. The same goes with culture. Cultural isolation historically leads to societies that lose technology, rather than perfecting technology. Cultural diversity, like genetic diversity, is almost always a good thing.

With that in mind, genetic and cultural differences do exist within the human species and we can learn a lot about our history, genealogy and evolution from these differences. Genes, languages and cultural traits often can be analyzed in similar ways. These analyses do not give identical results because languages, genes and cultural traits change differently. But similar analyses can be used and overlapping information can be obtained by applying all these methods. One can compare the development of pottery between two cultures, compare it with linguistic differences and similarities between those two cultures, and compare the genes of the people living in those two cultures and can from all that come up with some pretty good hints about how those two cultures developed over time and in relation to eachother.

One of the foremost expertis in doing this, using statistical methods I am unfamiliar with in my own work, but which my wife uses in studying climate, is Dr. Luigi Luca Cavalli-Sforza. He has done wonders analyzing the relationships between modern languages and the genes of modern populations and correlating the two to study human history and evolution. Some of his books are way beyond me, but I found Genes, Peoples, and Languages (2000) to be an amazing introduction into this field. I will refer a little bit to his work later.

First I want to start with some new research that indicates that our species, Homo sapiens, came very close to evolving into two distinct species in Africa right at the beginning of our common acestry.

Too often I hear people claim that humans have somehow gone "beyond" evolution or are "above" evolution or "escaped" evolution. Of course that is completely wrong. We are just as much a part of and affected by evolution as any species that has ever existed. The same hubris that has allowed us to ignore the impact of the environmental degradation we cause leads us to think our species isn't affected by the same natural rules that every other species that has ever existed is affected by. But we are animals and the same rules apply to us. And we can be studied in pretty much the same way any animal can be studied. And human evolution prior to the dominance of Homo sapiens was full of various human and human-like species that coexisted for millenia. The most recent coexistence was in Europe where the Neanderthals and our species lived side by side for tens of thousands of years. In Asia Homo erectus and Homo sapiens coexisted. And in Africa countless Australopithecine and Homo species coexisted for millions of years. The fact that there is only one human species alive today is very unusual.

I read about the recent discovery that modern humans nearly diverged into a South African and an East African species on BBC today:

Although present-day people carry a signature of the ancient split in their DNA, today's Africans are part of a single population.

The researchers compiled a "family tree" of different mitochondrial DNA groupings found in Africa.

A major split occurred near the root of the tree as early as 150,000 years ago.

On one side of this divide are the mitochondrial lineages now found predominantly in East and West Africa, and all maternal lineages found outside Africa.

On the other side of the divide are lineages predominantly found in the Khoi and San (Khoisan) hunter-gatherer people of southern Africa [sometimes called Bushmen].

Many African populations today harbour a mixture of both.

The scientists say the most likely scenario is that two populations went their separate ways early in our evolutionary history.

This gave rise to separate human communities localised to eastern and southern Africa that evolved in isolation for between 50,000 and 100,000 years...

The genetic data show that populations came back together as a single, pan-African population about 40,000 years ago.

This renewed contact appears to coincide with the development of more advanced stone tool technology and may have been helped by more favourable environmental conditions.

"[The mixing] was two-way to a certain extent, but the majority of mitochondrial lineages seem to have come from north-eastern Africa down to the south," said Spencer Wells.

Most people know about "mitochondrial Eve." As I wrote in my earlier diary, all human beings today can trace their mitochondrial DNA back to a common ancestor living in East Africa some 100-150,000 years ago, the so-called mitochondrial "Eve." What is striking is that this is almost the same timing of the near-split of humans into two species. So we have a common ancestry, going back to the ancestral Eve, then relatively soon afterwards we had a major split into the Koisan (Bushman) ancestors, and the ancestors of the rest of us (roughly speaking...but remember these two groups did come back into contact before any of our ancestors left Africa).

In retrospect this isn't too surprising to me. I had long ago realzied taht the divergence of the ancestors of the Bushmen (Southern African) and the ancestors of the African Pygmies (Eastern African) seemed to be be the very first ethnic division in human history since we first started diversifying after mitochondrial Eve. And the rest of us probably share that ancestor of the Pygmies. The new data just shows far more clearly what was previously noticed more roughly.

A similar analysis using modern Y-chromosomal DNA (traced only through the male lineage) showed that all men alive today can be traced back to a common grandpappy in East Africa some 60-90,000 years ago. Interestingly, the common male ancestor of all humans was from DURING the South/East Africa split. This suggests that we share a common female ancestor from before the split, but our common male ancestry may come from only one of the two groups, Southern or, more likely, Eastern African. An alternative is that the split was only among females and males intermixed, but this seems highly unlikely.

There is nothing special about analyzing the Y-chromasomal and mitochondrial DNAs. Truth is, you can do the same kind of analysis with ANY piece of DNA in the body...it just is much harder to do than with the mitochondrial or Y-chromosomal DNA. But statistical analyses have shown that all of us can trace our DNA molecular patterns back to some 86,000 common ancestors. Those roughly 86,000 people, from different places and different times (though mostly probably from Africa since that is the place of our common descent) are our shared genetic heritage.

Another interesting aspect of this was that the reunification of the South and East African branches coincided roughly with a sudden surge in human creativity around 50,000 years ago. When the split happened, the humans of 150,000 years ago weren't quite what we are today. Physically they would pass. But culturally, and presumably in terms of how the brains worked, they were different. Stone tools made from our earliest tool using ancestors, Homo habilis, some 2.4 million years ago, up to even early Homo sapiens, tended to be slow to change and tended to be similar over wide areas. This doesn't mean things stayed the same throughout that period. Far, far from it. Over nearly 2.4 million years things changed a lot, but the pace of that change was slow and regional variation was small. It was almost as if we were doing simply a glorified version of Chimpanzees removing leaves from a twig to use the twig as a tool to get termites from a termite nest.

Then starting sometime around 50,000 years ago, well after we physically evolved, and right about the reunification of the two branches that nearly diverged into two species, something changed. Suddenly there were many more innovations in tools and far more regional variations. Complex culture seemed to suddenly evolve. Art started to evolve, culminating in the Cro Mangon art of Alta Mira and Lascaux. (As an aside, one theory, though one I consider shaky so far, is that the modern Basque are fairly direct descendants of this Cro Magnon culture...there is some genetic evidence for this, but...). Some kind of goddess or fertility cult seemed to start to appear, with widespread appearance of carved female figures called Venus figures. This was the start of a tradition that seems to have been carried even into the Bronze Age. And people started spreading out over the globe. To me it seems like we suddenly evolved imagination starting around 50,000 years ago. Was it a change in our brain structure? Was it a breakthrough in language? No one knows. But maybe simply the mixing of the South and East African branches brought together two separate culural traditions sparking something of a cultural competition or mutual inspiration between the two traditions. After all, like I said earlier, genetic and cultural diversity is almost always a good thing. You can almost think of it in terms of capitalist ideas of competition. A population in isolation has little reason to innovate. Add rival groups and the need to innovate becomes a matter of survival.

Or it could be the similar timing of the reunification and the cultural innovation was mere coincidence. But somehow I doubt it.

After this reunification of the diverging populations and the sudden surge in creativity, humans spread across the globe, creating a much larger diversity of cultures and eventually ethnicities. This led to the near isolation of some populations while the core population remained fairly genetically mixed. However, the process of expansion of population and geographic distribution led to another period of genetic diverification which could have led to another period of near speciation. This second period of more rapid human diversification was much more recent and much shorter lived.

Evolution is driven by two things: population size (since the larger the population the greater the genetic diversity) and distance (since larger population distribution allows greater divergence). It used to be thought that once we evolved to be Homo sapiens we largely stopped evolving. Recent data shows this isn't true. It seems that around 5000 years ago human evolution, presumably because it had reached a critical size and large distribution over most of the globe, suddenly sped up. We can't tell if we are diverging more than ever right now, or if, once again, perhaps due to the bridging of those large distances through modern transportation, we are evolving slowly. The techniques used can't see events closer than about 5000 years ago. I suspect that as empires grew, steppe nomads swept across continents, and transportation improved, genetic exchanges increased across our entire population, more or less, to counter act the speed up in human evolution. However, some pockets of people in places like Australia and New Guinea would have been largely genetically isolated for millennia up until around the 18th century. So perhaps any slow down in the pace of human evolution would only have started a few hundred years ago.

This means that from a common ancestor some 150,000 years ago, we went first through about 100,000 years of divergence almost into two species (perhaps heading towards, but not quite reaching, something like the split between the Chimpanzee and the Bonobo). Then from about 40-50,000 years ago until about 5000 years ago, population size was small enough and our global distribution narrow enough, at least early on, that we were evolving slowly. Then around 5000 years ago our population size and distribution becames such that we began diverging again, probably towards (but never actually becoming) several subspecies. This second period of divergence probably was short lived because of innovations in transportation (starting with the horse, then sailing ships then airplanes) which probably (though this cannot be currently tested) have stopped this second divergence within the last several centuries.

Luigi Luca Cavalli-Sforza's studies of languages and genes almost certainly reflects all of these trends: the near divergences 150,000 years ago, the reunification, the second divergence 5000 years ago, and whatever is happening right now. But we don't yet have enough information to connect his studies with these more recent, and broader, studies. Cavalli-Sforza points out that you can statistically distinguish the genes of people in to neighboring villages in Italy. This is an amazing level of resolution, even if at that level the information is nearly meaningless. But it shows how powerful the technique is. But the same techniques can show genetic affinities among larger groupings. Almost every population on earth can be fitted into genetic groups and the timing of the divergences can be calculated. This is the meat of what he covers in Genes, Peoples, and Languages. Here is an image of a "family tree" (a version called a "rootless tree" generally favored by modern evolutionary biologists) of modern human populations based on a statistical analysis of their genes (from Cavalli-Sforza's book via Wikipedia):

A similar analysis is also covered in much a more popularized and less scientific manner in The Seven Daughters of Eve (2001) by Bryan Sykes looking only at mitochondrial DNA. (Sykes also has a sequel about the Y-chromasomal DNA, but I haven't read it yet). I am betting that if studied carefully, the earliest divergences seen in the Cavalli-Sforza analyses could fit well into the divergence 150,000 years ago, and one can find some of the more recent divergences would fit into the more recent period of divergence 5000 years ago. There may also be hints of other divergences between the two that have not yet been detected.

I love how the rough outlines of human development are being filled in. But there is still a long way to go. Ultimately we all come from the same pool of about 86,000 common ancestors. And humans could still evolve into separates species if conditions for genetic isolation ever occurred (reminding me of very interesting science fiction books like Hyperion by Dan Simmons, and Skaith trilogy by Leigh Brackett, who also was a scriptwriter for movies like The Big Sleep and The Empire Strikes Back). It isn't likely to happen right now when people can meet on the internet, then hop on jet planes and have sex with people across the globe. But human evolution is still an ongoing story.

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