Denisovans

Denisovan Brains, Science, Media, Anthropology

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DenisovansUpdate November 2012: In addition to the Denisovan complexities described below, see My ancestors, myself by Jonathan Marks, in the recently launched Aeon Magazine. Marks writes: “My feeling is that the Denisovans are a reification as well, built from genetic data, biological deduction, and anthropological assumption.” It’s a feeling I’ve come to share, as I suspect some of the Denisovan complexities may be a result of our speculative analytical techniques outrunning the archaeology, which may yet have more to reveal on this story.

Denisovans! One funny thing about this blog is that it’s been in the forefront of reporting Denisovan admixture and how to interpret and present Denisovans anthropologically. It began with Denisovans, Neandertals, Anthropology 101 which eventually became the content sections Denisovans, Neandertals, Archaics as Human Races and More Mothers than Mitochondrial Eve.

So every time there’s a new Denisovan paper, people land here. Today was one of those days. The paper is A High-Coverage Genome Sequence from an Archaic Denisovan Individual and as John Hawks reports Denisova at high coverage, this is exciting technology and very cool research. But it’s also very complex and is going to require us to reinvestigate the archaeological story.

I also agree with Razib Khan’s comment on Deep dive into the Denisovans:

I think population movements in near and far prehistory significantly obscure our comprehension of the patterns of past genetic variation. One reason that the Denisova hominin presents conundrums (e.g., how did Australians and Melanesians admix with a population whose only remains are found in Siberia) is that we’re viewing it through the lens of the present. What other lens can we view it through? We’re not time travelers. But we should be perhaps more conscious of the filter which that imposes upon our perception and model of the world. This is probably a time when it is best to have only a modest confidence in any given proposition about the prehistoric past.

It is best to have only modest confidence.

What bothers me about Denisovan coverage are headlines like Brain genes differences mark ancient Denisovans. In this USA Today piece:

Whether the genes that modern people possess which were absent in Denisovans’ genome account for modern people’s success remains unclear, Svante Paabo notes. “And it’s quite interesting for me to note that eight of them has to do with brain function and brain development, the connectivity in the brain of synapses between nerve cells function, and some of them have to do with genes that, for example, can cause autism when these genes are mutated,” Paabo says. “So I think that this is perhaps in the long term to me the most fascinating thing about this, what it will tell us in the future about what makes us special in the world relative to the Denisovans and Neandertals.”

The problem with statements like that would seem obvious. This article is using terms like “primitive humans” and Paabo is talking about Denisovan brains. But it’s also telling us that Denisovan admixture only shows up in Australia and New Guinea, not in southeast Asia.

Do these scientists and journalists have any idea of the possible racist interpretations lurking in such statements? It is not an accident that attempts to refute Race/IQ plasticity often turn to the Australian aborigines as a final appeal. This appeal is also consistent with the hardening of 19th-century race ideas with British colonialism in Australia–see Race and the Crisis of Humanism and the section on Anthropology and Human Nature.

Fortunately in the longer Scientific American article, New DNA Analysis Shows Ancient Humans Interbred with Denisovans, John Hawks contributes a much-needed dose of realism about this Denisovan brain stuff:

Hawks counters that it might be a little early to begin drawing conclusions about human brain evolution from genetic comparisons with archaic relatives. Decoding the genetic map of the brain and cognition from a genome is still a long way off, he notes–unraveling skin color is still difficult enough given our current technologies and knowledge.

But the headline remains–Denisovan brain differences, admixture only showing up in Australia & New Guinea. It’s a great recipe. I’m just waiting for the next Nicholas Wade article that calls Denisovan admixture “interracial marriage.”

In the meantime–please be circumspect with Denisovan brain speculations. Take care when launching scientific speculation into the media.

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  • Very well written and scholarly article. This would seem to contradict Mitt Romney’s belief that we originated in a different star constellaton.

    http://www.youtube.com/watch?v=IGFAph3lWqw

    • Thanks–indeed, I should clarify that these are debates *within* the over-arching and accepted theory of evolution, not anything that would challenge evolutionary understandings. For some other thoughts, see Jared Diamond won’t beat Mitt Romney.

  • Pingback: Denisovan Brains, Science, Media, Anthropology | Anthropology & Journalism | Scoop.it()

  • Michael Nowacki

    I hope you monitor your old posts…

    Over a decade ago I first received a presentation of the Mitochondrial Eve evidence in a faculty lecture at a small college. The main points I remember are:

    1: Roughly 75,000 years ago there was a world-wide population die-off (possibly linked to a gigantic volcanic eruption) that reduced the entire human population to a very small number, less than 2000 individuals.
    2. The surviving populations of the event, termed a bottleneck, are not merely the direct ancestors of all subsequent people; the survivors were all direct descendants of a single mitochondrial lineage, this actual Mitochondrial Eve having lived several thousand years earlier. But in any case, it was ONLY that matrilineal line that made it past the bottleneck.
    3: I never see reference to this final point. DNA analysis is able to determine that functionally identical proteins are “spelled” differently in differing individuals. That is, this is a genetically determined individual difference.This difference in no way defines anything close to a separate or sub-species, but is a way to trace breeding populations. An example was: using databases available to professionals, it is possible to identify where on the entire Rocky Mountain range a specific individual deer originated, because the local populations have been identified by this variation in protein spellings. Same with salmon in Atlantic and Pacific populations.

    Further, it is now a routine way to identify breeding populations among many species to note these protein spelling variations. Which happens to illustrate that there is a certain degree of genetic diversity among living species, which unlike humans, have multiple mitochondrial lineages.

    The significant detail is: humans world-wide, no matter what their “race” , morphology, ancestry, etc., etc., show much less variation along this dimension of protein spelling variation than any other documented species, by a wide margin. That is, ALL surviving humans populations are much more closely related (in what we call family) than any other known species.

    Is this rendition accurate? If so, is it not important for understanding humans as we have actually evolved? Is this exceptional heterogeneity an interesting factor? Would it not suggest that the extreme similarity among individuals in a large group might be a potential reason that only the Mitochondrial Eve lineage survived and increased its population, unlike any of the ancestral families?

    Thanks in advance for any reply you can offer.

    MN

    • Thank you for posting here. I don’t know if this rendition is still accurate, but I’ll try Twitter and Facebook for help.