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Lookin At Our Cousins

 

This month the Museum takes a further look at our Cousins.

Exhibit One:

We’ll start with the Denisovans. What do we know? Well, it’s not exactly a complete skeleton as we’ve recovered a bit of finger bone, three teeth and a toe bone. DNA extracted from a tooth placed them outside the Neanderthal and Our genomes, and it seems to carry through to some modern human populations, the Polynesians for instance, and in the Neanderthal Genome as well. So the whole family was on friendly terms with these cousins, who seem to have more in common with Neanderthal than us, although current charts have them branching off the Homo line earlier than either, and their genes lines are further from Neanderthal that Neanderthal is to us. There seems to have been strong contact with Neanderthals as some of their bones recovered from the same cave have up to 17% Devonian DNA. There are some caveats however, as the cave was also habituated by Us, though it is assume not all at the same time. Has this contaminated the DNA samples? There is a possibility, but the findings seem strong based on what we have. Indeed they are finding traces of the Denisovan genome in Neanderthals discovered in Spain. They have also found what maybe the oldest recovered needle at the cave, dating around 50,000 BCE, but again with all the traffic in the cave, precise dating and who used this needle is somewhat problematic. What would be nice is to find a Denisovan home site, with lots of bones including a skull, and associated tools. Then we could really fit them into the story of Us. It is important to remember that although it seems to happen all the time, finding a fossil is actually very rare, and there is some possibility that we have found all we ever will of this cousin, but it is to be hoped not. Another possibility is that they were so similar to Neanderthals that separating the two will be almost impossible if over time they were incorporated in the Neanderthal line, maybe before we came out of Africa.

Exhibit Two:

As for Neanderthal the Museum assumes we all know something about them. From their genome and other factors we now know that we had a common ancestor around 400,000 years ago. From there they stayed in the North while our branch made Us in East Africa. In the “out of Africa” scenario we came back out of Africa around 60,000 years ago (plus or minus a lot) and there we met Neanderthal, and evidently the Denisovans, still in place. But also in that time frame, some 70,000 years ago, there was a possible defining moment for our genome in the form of the Toba Super-Eruption in India which seems to have led to the much commented on lack of diversity in our genome except of course for West Africans. A European has more genes in common with someone from China, than a West African has with his neighbor. This same lack of diversity is found in the Neanderthal genome after that time as well.

Obviously we can know very little about the culture of Neanderthal, other than that in the fossil record they don’t seemed to have changed much in their 300,000 years and some people have used this as a slur against them, all that time and no “advancement”. On the other hand the Us in Africa spent those same 300,000 years in much the same way. It was after we moved into the North again that “cultural” change shows up in the record. There is no doubt about two things, Neanderthal did not continue with Us, and we developed agriculture and from then on dominated our world. Was this relatively sudden change cultural? It has been posited that Neanderthals were not able to form social network larger than the “clan”, a family group in the local area a hunter-gatherer community needs to survive. Their artifacts show very little trading with other groups outside their territory, and there is an uncomfortably common sign of cannibalism in the sites we have found. We look at Chimps and Bonobos and find the Chimps defend their territories and Bonobos do not. This is directly related to Testosterone levels in the populations, and the argument is that the same was true for Us and our Cousin. We came in and established vast trading networks unknown to Neanderthals which shows a cultural interaction they never achieved. Does this bespeak of a situation that Neanderthals lived in “Troops” like Chimpanzees, and We came in “Tribes?”

This is not to say that We have a non-violent past, far from it, but if we had superior social networks, our competition for resources, sometimes very limited resources, with Neanderthals would have been uneven. The few remaining hunter-gathering tribes we have can certainly be called dangerous compared with our larger societies, but they are not in a state of constant warfare either. They are Us, indeed they probably represent what We were like for a vast majority of the last 100,000 years better than We do now, and use social interaction as much as or more than violence to get along with their neighbors.

But whatever the reasons, and they are sure to be plural, not singular, the Neanderthal line slowly diminished until failing at last about 40,000 years ago. It is a mistaken notion that going extinct is somehow a mark of unworthiness for a species, for by far the story of complex life on earth is one of extinction, not abundance. Of all life on earth the ancient single-celled beasties are by far the most successful, and still hold in their tiny little hearts the ability to kill all of the more “complex” life on Earth if the environment changes in their favor. How fragile are the conditions that support complex life on this tiny rock flying through the vastness of the universe.

At the Exit:

 The Museum (and everyone else) must thank Svante Pääbo for most of this DNA centered work, as he has led the way for using genomes to discover history.


Unkwil



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Uncle Willie loves to have feedback from both readers who appreciate his point of view as well as from missguided souls who disagree.