Human evolution: What the Dmanisi fossils tell us about who we are
The history of human paleontology can be viewed as a relentless battle between lumpers and splitters. Wikipedia claims Charles Darwin himself originated the terms in 1857: “(Those who make many species are the ‘splitters,’ and those who make few are the ‘lumpers.’)” It seems only fitting.
The splitters took their lumps this week, with publication in Science of the 1.8 million year-old completely preserved adult hominid skull, the oldest yet discovered. It, and several other hominin fossils–a toothless old man, two adult males, a young female, and a teen whose sex remains undetermined–are from the extraordinary Dmanisi site in Georgia. Ann Gibbons’s piece in Science explains.
Razib Khan translates the paper at Gene Expression: “[Y]ou might say that this publication burns down the ‘bushy’ model of human origins, where you have a complex series of bifurcations and local regional diversity, and then rapid extinction with the rise of H. sapiens sapiens ~50,000 years ago.”
The people found at the Dmanisi dig appear to have been the prey of large carnivores. The scientists who have been studying them believe they probably all lived in the same rough time span of about 200 years. Which has led the scientists to lumping, declaring them all probably Homo erectus. “Dmanisi provides the best window we have as to what normal variation looks like in the early Homo fossil record.” says paeontologist and lumper Adam Van Arsdale at the Pleistocene Scene.
What does normal human variation look like?
The five individuals are very different from one another in shape of cranium and heaviness of features. So different that if they had been found in geographically different locales, they might well be classified as different species–even though present-day people vary just as much. Paleoanthropologist and lumper John Hawks notes that the Dmanisi skull D4500 had a small brain, 546 ml, about the same as brains of large male australopithecines. “Yet despite the small brain we have little trouble recognizing the strong H. erectus-like morphology of D4500 in the face and masticatory muscle configuration.”
And this implies that many early Homo fossils in Africa should really be classified as H. erectus too. Says Van Arsdale, “All the fossil variation that in East Africa gets divided by some into Homo habilis, Homo rudolfensis, Homo ergaster, and Homo erectus, because the specimens are too variable to represent a single species, viewed from Dmanisi, suddenly look like a single evolving lineage. Or at least, make it harder to reject that idea as a starting hypothesis.”
Why splitting and lumping in human paleontology?
Khan again: “The reason these sorts of findings overturn the orthodoxy has more to do with human cognitive intuitions about why things are categorized, than the reality of how nature arranges itself.” There’s the human passion for pattern recognition to contend with, so strong that it imposes patterns even where there aren’t any. And the natural inclination among fossil discoverers to split (and name the splitted thing) as a way of taking ownership of the fossil discovered. In addition to personal satisfaction, this can confer substantial opportunities for personal profit.
I wonder too about the effect on the human psyche of the idea of a single line of descent that results in polyglot humanity with all its different sizes and shapes and colors. Assume this unitary notion trickles down through the decades and becomes the conventional way of thinking about how we came to be. (Not counting creationists, although it suddenly occurs to me that I have never heard how they account for H. erectus, Australopithecus & Co. If you know, pls leave an explanatory comment.)
Would accepting that we’re the products of a single line of descent make us less xenophobic? Would it make war less acceptable–and less frequent? Would it be easier to Love Thy Neighbor? Or at least not hate him because his skin is a different color–or even for no particular reason?
The splitters fight back
Although several prominent paleoanthropologists lean toward lumping, the splitters haven’t abandoned the field of battle. The Gibbons piece describes what some of them say. Michael Marshall also samples splitter thoughts at his account in New Scientist. See also Charles Choi’s news story at LiveScience.
At The Conversation, human evolutionary biologist Darren Curnoe declares the idea of a single line comprising only two species, H. erectus and H. sapiens, “wildly premature.” He attributes it in part to the headline-grabbing tendency of science today, and he won’t get any argument from me about the reality of that.
But he is troubled for technical reasons too, in particular the paper’s reliance on 3-D computer analyses of the fossils. Computer reconstructions “often fail to detect the subtleties of species differences, especially among genetically closely related groups like the species of Homo.” He also points out that the environment–for example nutrition and disease–can have dramatic effects on traits like skull shape.
At the Mermaid’s Tale, Ken Weiss recalls his grad student days at the University of Michigan, then home to what he calls hyper-lumpers. But about Dmanisi he sounds like a bit of a splitter. He concludes, “Single-species may be right or it may be wrong, but conclusions are being jumped to with rather minimal theoretical underpinning. At 1.8 million years old, there will be no DNA to ride to the rescue.”
Dang, he’s probably right about our inability to recover DNA from fossils that old. But I have learned, in decades of writing about science, to never say never. So I continue to hope otherwise. Hard not to be dazzled by the things really ancient ancient DNA could tell us.
Will Dmanisi rewrite the textbooks on human evolution?
Ricki Lewis writes textbooks and has the tangled task of keeping up with all this from edition to edition. At DNA Science, she gives us a bit of historical perspective on the splitter-lumper battles since the 1980s and regards this episode as just one more example of the way science works, and should work. She says, “New results force us to re-evaluate what we thought we knew, and we can’t predict what technologies not yet invented will enable us to see.”
OTOH, maybe Ricki won’t have to do much rewriting after all. At How to Think Like a Neanderthal, Frederick Coolidge and Thomas Wynn sniff that the D4500 skull “is unlikely to warrant more than a brief mention in an introductory course on human evolution.” They are more interested in a different Dmanisi skull, the skull of the toothless old man.
He survived for some years without teeth, so he must have had help. I’m speculating here, but that would be help from people who pounded (or chewed) meat and plants into a paste that he could swallow, or maybe cut them into tiny pieces and cooked them very soft in soup. I can’t recall whether there’s any evidence for cooking that long ago, and I don’t feel like looking it up right now on deadline. But you get the picture. People need teeth to eat, and if they don’t have them, they need assistance. In any case, the fact that an old man could hang in there without teeth for some time tells us something pretty interesting about human social relationships 1.8 million years ago.
More on gossip and scandal in science blogging
Last week I wrote at length about the events surrounding sexual harassment scandals in science blogging. Among other shocks to the system, the week featured testimony from a number of women bloggers that Bora Zivkovic, arguably the most prominent–and powerful–man in science blogging, the man who built the SciAm blog network and co-founded the annual ScienceOnline conference, had pursued them, mostly verbally. It was a week of fraught announcements and accusations and taletellings and the pulling down of idols and firings and horrified disbelief and even more horrified acceptance. This week science bloggers moved on to thoughtful analysis.
Martin Robbins’s post addresses a perennial issue familiar from politics: What Did They Know and When Did They Know It? Robbins says a lot of people knew, and his reasoning is persuasive.
I was one of them. I knew a year ago, in October 2012, when I read Monica Byrne’s original post describing her experiences with Bora. She didn’t name him as the perpetrator until she reposted on October 14 of this year, but to those who know a bit about the science blogosphere, she supplied enough detail in her first post to make his identity obvious.
The dirty little secret was not so secret after all
I heard no more until the lid popped off last week. Apparently word did get to SciAm a year ago, and there was talk, and he apologized. If Byrne had not named him, Robbins says, “other women would not have been given the confidence to speak out too, Bora would not have made his public admission, and SciAm would not have been forced to issue a statement acknowledging their failed 2012 ‘investigation’. Bora would remain a key figure at Science Online and Scientific American, and an unknown number of women would have continued to suffer in silence. We know this would have happened, because it DID happen for the last year.”
He also points out that it should have been easy to infer that Monica Byrne’s was not the only example. “Harassment, like other forms of abuse of power, is rarely a one-off. Every shred of evidence we have on this problem in society shows that offenders tend to be predatory recidivists, acting out the same pattern again and again over years or even decades. They rely on the silence of others,” Robbins says.
Christie Wilcox is surprised that folks have been surprised. She tells us she has been hearing these stories about Bora since her first ScienceOnline meeting in 2010. She has not been a recipient of Bora’s unwanted attentions, she notes, although he aided her blogging career substantially. “I am a little dumbfounded at how surprised the community is by all of this—how so many people missed what seemed to me at the time to be common knowledge.” She wonders if she should have said something. She wonders if she has just become numb to this sort of thing because it has happened to her so often. It has made her, she thinks, a bad ally for other women who have been in that boat.
Scicurious, a very prominent blogger mentored by Bora since 2008, says she never encountered this behavior from him, apparently had no idea it was going on, and was devastated by last week’s revelations. But for the blogging community’s reactions she has only praise. At Neurotic Physiology she says, “Yes, people fought, and jumped to conclusions, and etc. But there have been no death threats or rape threats, and compared to some communities I’ve seen…well I’m impressed.”
Many comments on her post, some noteworthy. It’s nothing to do with sexual harassment, but see in particular Razib Khan’s stories about the power Bora wielded in the blogging world and how even Khan–one of the best-known science bloggers (Gene Expression, long part of the Discover network), and one who did not owe his position to Bora–was careful not to run afoul of him.
Alice Bell considers the effect of these stories on the science blogging community at Through the Looking Glass. She writes about hidden support, the informal networks that circulate warnings about creeps: don’t get into an elevator alone with this guy, and if you have a meeting with that guy, watch out for his wandering hands. It’s just gossip. But helpful gossip, getting information to where it’s needed in situations where public disclosures would get only the discloser in trouble. She recognizes its limitations, though. “We support each other in these ways, but in doing so support the oppressors too.” Lots of comments, some argumentative.
What SciAm bloggers say
Bora put together the SciAm Blog Network, so let’s hear from a couple of SciAm bloggers. Ashutosh Jogalekar, who blogs at Curious Wavefunction, makes Bora’s power clear in his praise of what the man did for science blogging in general and the SciAm network in particular. The network now numbers dozens of bloggers, and Bora pretty much built it himself. Jogalekar decries Bora’s sexual harassing but also points out “one thing we should note is that in none of the three cases did Bora’s behavior descend into overt sexual or physical harassment.” As you may imagine, the commenters tend to be unhappy at this mini-exculpation.
Also unhappy was another SciAm blogger, Jennifer Ouellette of Cocktail Party Physics. Hers is a long, very pained, post followed by a number of argumentative comments. But I want to emphasize her take on harassment-by-conversational-insinuation, quite different from Jogalekar’s: “I would argue that the insidiousness of those borderline gray areas can sometimes be more damaging, in the long run, than the blatantly obvious cases — particularly for fields that wish to attract and promote more women within their ranks.”
Indirect propositions and conversational innuendo
The “borderline gray areas” are a very knotty problem indeed. First of all, they are as common as dirt. For every outright proposition, women (and some men) are on the receiving end of several innuendo-laden conversations. The sexual message is the subtext, but it’s perfectly clear.
“Knock it off” may be the right response in some cases. But what if the woman is young and powerless and the man is in a position to hurt her career–or her life? Advising her to just say “knock it off” is useless here. Counterproductive, even.
What is the right response? Is there any way to fend off this kind of indirect advance without giving offense, without risking damage? All week I’ve been thinking about this, and reading what others say in tweets, on science-writing listservs, at blogs. Not only are there no easy answers, there don’t seem to be any answers at all.