Why we should be excited by 100,000 year old human teeth from China

October 15, 2015 • 7:10 am

by Matthew Cobb

I told you all the other day – discoveries in recent human evolution are appearing at an astonishing pace. I just gave my final lecture of the year to the students on the first year Genes, Evolution and Development course at the University of Manchester; last night, at around 23:30, I had to change the lecture because of a discovery that had just been reported in Nature.

47 teeth, clearly from modern humans, have just been found in a massive cave system in southern China. They are dated to over 80,000 years ago – the date range is 80-120,000 years. There were no tools associated with the find, so the researchers asssume that people were not living in the cave system, but rather these teeth came from bodies that were dragged into the caves by large predators (hyena bones were also found). Here are the teeth – these could have been pulled from your mouth (although they probably show less decay than would be in your teeth – much less than in mine!).

Photo: S. Xing and X-J. Wu (Nature).

Why is this a big deal? Because we weren’t supposed to be there at that time. Although there was archaeological evidence of humans having left Africa at around this time – there are traces of 100,000 year old human settlements in Israel – it had been argued that the expansion never got any further, and that the key wave of migration took place around 50-60,000 years ago.

These 47 teeth show that humans successfully left Africa and colonised an important part of the planet, tens of thousands of years earlier than we thought.

This figure from Liu et al (2015) shows the location of the material in the cave system:

a, Location of the Daoxian site. Late Middle Pleistocene and Late Pleistocene localities with human remains that have been included in the morphological and/or metric comparison with Daoxian are also marked on the map. 2: Tianyuan Cave; 3: Huanglong Cave; 4: Liujiang; 5: Zhiren Cave; 6: Tubo; 7: Xujiayao; 8: Luna; 9: Chuandong; 10: Malu Cave; 11: Lijiang; 12: Longlin; 13: Huli Cave; and 14: Xintai. The map is adapted from the original Chinese map from National Administration of Surveying, Mapping and Geoinformation of China (http://219.238.166.215/mcp/index.asp). b, General view of the interior of the cave and the spatial relationship of regions IIA, IIB and IIC, with some of the layers marked. c, Plan view of the excavation area. d, Detail of the stratigraphic layers of region II of the Daoxian site. All human fossils come from layer 2.

The key question now is what happened to that first wave of migration – did they die out, or did they meet up with subsequent migrants and exchange their genes? For the moment, there is no DNA to be analysed from these teeth. Furthermore, if people went to China, why didn’t they also spread up into Europe at this earlier date? We are confident this is not the case, because all the archaeological evidence argues against it.

Maybe Western Eurasia was too full of Neanderthals at the time, and it was only later, around 50,000 years ago that it was ecologically possible for hunter-gatherers to spread northwards – this would suggest that when we did successfully colonise Western Eurasia, either the Neanderthal population had already diminished for unknown reasons, or we had decisive cultural advantages that enabled us to rapidly spread into their areas.

As I said in a previous post, if I had my time over again, this is the area of science I would study. It is simply amazing.

This infographic from Nature sums up the new way of thinking:

 

References:

Callaway (2015) ‘Teeth from China revea early human trek out of Africa’. Nature website

Liu, W. et al. ‘The earliest unequivocal modern humans in Southern China’ Nature http://dx.doi.org/10.1038/nature15696 (2015).

David Koch and the Hall of Human Origins

October 7, 2010 • 12:42 pm

by Greg Mayer

PZ noted my and Jerry’s pieces on the new Hall of Human Origins at the USNM, and one of his commenters, DavidCOG, points to this piece at Climate Progress (based in part on Jane Mayer’s (no relation) New Yorker article on the Koch brothers), which in turn points to a couple of  items at Think Progress, and this by Matt Yglesias (among others). In summary, these pieces detect a much more sinister motivation for Koch’s funding of the exhibit, flowing from his global warming denialism. As I’d noted in the comments on my piece, there is material about climate change in the exhibit, but nothing I regarded as untoward. The scale of climate change discussed in the exhibit– tens of thousands to millions of years– doesn’t seem relevant to the decade to century scale of current warming. And, there is, as far as I saw, no discussion of current warming in the exhibit.

Perhaps Koch wanted the point made that climate does change, and that this influenced human evolution– that’s true of course– and he hoped that, by non sequitur, visitors would conclude that recent rapid climate change is nothing to worry about. But that is a non sequitur, and a fairly subtle one at that, so I’m not sure he’s getting his money’s worth. I’ll let Climate Progress make the argument for its view in their video.

PZ has now commented directly on the issue.

The Hall of Human Origins at the National Museum of Natural History

October 5, 2010 • 9:53 pm

by Greg Mayer

The Hall of Human Origins, a new permanent exhibition at the Smithsonian‘s National Museum of Natural History (aka the USNM) opened last March (at which time I got only a peek), and over the summer I finally got a chance to take in the whole exhibit. Like Edward Rothstein of the New York Times, whose review I noted in an earlier post, I have somewhat mixed feelings. There are many excellent displays in the hall, and it does bear “repeated, close viewing” (which is to my mind the highest praise for a museum exhibit), but there are also lost opportunities, slack use of space and objects, and, frankly, abdication of curatorial responsibility.

As I’ve mentioned in earlier posts, I’m a fan of the “cabinet” style in natural history museums. This style emphasizes well-labeled displays rich in the number and diversity of specimens and objects on display. An alternative style, which I’ve taken to calling “interactive”, is characterized by sparse specimens, large fonts, blank space, and interactive displays. Along with the late Steve Gould, I’m less fond of this style. First, some of the good stuff. The hall opens with a number of reproductions of well-known hominid skulls, such as this Paranthropus boisei (one could quibble with some of the taxonomy adopted in the exhibit, but it’s not a major concern of most visitors, and I’ll use what’s in the labels). For complex three-dimensional structures, such as skulls, the ability to walk around, look under, and touch the object greatly enhances the visitor’s grasp of the object, and I applaud taking some of the skulls out of the display cases, and putting them into the hall and the visitor’s hands.

Paranthropus boisei, KNM-ER 406

The following two skeletons, nearly complete, of Homo erectus and Homo neanderthalensis, are well-labeled, and, placed side-by side, allow the visitor to compare and contrast their form, while the signage guides the eye to particularly interesting parts, and their interpretation.

Homo erectus (left) and Homo neanderthalensis

The exhibit includes a number of life reconstructions of hominid heads by John Gurche. Any life reconstruction must be a work of art as well as science, and is, of necessity, in part speculative. Gurche is well-known for making his art as informed as possible by science, and the fact that corresponding skulls for most or all of the life reconstructions are in the exhibit allows the visitor to compare the art with the inspiration.

Paranthropus boisei (skull pictured in first photo in post)

I also liked some large bronzes scattered about, which, like Gurche’s life reconstructions, are both art and science, and, like the skull casts, walk-aroundable. They reminded me of Carl Akeley’s famous bronzes, found at museum such as the Field in Chicago, and the American Musuem in New York.

Mother and child

Paleoanthropological materials (bones, tools, art) are sufficiently rare that even great museums like the USNM must rely on reproductions for most of the display materials. This is a disappointment, but understandable.

Ancient art works-- note that they are all casts

But some aspects of the hall, generally those in the more “interactive” style were less successful to my mind. Here is the theme of the hall–  “What does it mean to be human?”– which to me seems an ill-formed question, not subject to any clearly comprehensible response. I was tempted to say, “Fortytwo.” Note that the exhibit designers quickly translate the theme to a different, and more answerable, question.

The hall's theme.

Some early parts of the hall don’t seem to make good use of the space available.

A really lost opportunity is presented by a “cave wall” with fine reproductions of cave art, but little or nothing to guide or inform the visitor as to the import of what is displayed. There is some interpretive signage, but it’s in another case, not closely adjacent. As Edward Tufte has urged, we should integrate our images, words, numbers, and –for museums– objects; keeping all within an eyespan. These are thrilling achievements by among the earliest of human artists, but we are given little to go on in interpreting them, and our appreciation stays at a purely aesthetic level.

Horse and hands
Lion (?) heads

The part of the exhibit I found most wanting is the reproduction of a famous cave painting known as “The Sorcerer”, an anthropomorphic figure that combines deer and man.  The reproduction is fine.

The Sorcerer

But the signage (enalrged below) is not fine. The question “What do you see?” reflects a trend in pedagogy and museum display that is thought to be ‘active’, and ‘inquiry’ based. But you can’t make intelligent inquiries into something about which you know nothing. Are those the antlers of a caribou or a red deer? Are the dark markings in the leg similar to the bones or the muscles? And do they look like parts of a deer or of a man? What other paintings, if any,  are on this wall? Have any artifacts or bones been found in the cave? What animals lived in the area at the time? Without addressing these and many other questions, your inquiry goes nowhere. You may have an opinion, and it may feel good to have your opinion asked for, but your opinion is worthless– it is an uninformed speculation at best. The curators have abdicated their responsibility to provide the necessary context, and to share with us their informed opinion. They may of course be wrong, and further discoveries or reflection might lead us and them to another interpretation, but this does not excuse them for not letting us know what they think. I do not want to know what the visitor next to me sees, or even what I see; what I want to know is what is seen by the men and women who have studied this painting and its context most thoroughly, and reflected on it most deeply.

What do you see?

There are of course the now requisite interactive displays. (Note the question on the right!) Jerry has been to the exhibit on his current east coast tour, and he will likely have more to say about this aspect when he posts about it.

Can the concept of evolution co-exist with religious faith?

Overall, I’d give the exhibit a B- ; it does, as Edward Rothstein said, repay close and repeated viewing, but it could have been more.

An odd item I’ll close on are the curious politics of David Koch, chief funder of the exhibit (it’s actually called the David H. Koch Hall of Human Origins). As I noted before, he’s a global warming denialist, and, as Frank Rich of the New York Times recently detailed, along with his brother, he’s a major funder of the tea party movement. Since tea partiers tend to be creationists, this is a real head scratcher– what is Koch thinking? The people he’s funding would probably want the USNM shut down. (I did keep an eye out for anything about climate in the exhibit, but noticed nothing untoward.)

Jerry as a Neanderthal

September 27, 2010 • 3:22 pm

by Greg Mayer

At the new Hall of Human Origins at the USNM on the Mall in Washington D.C., you can have a photograph of your face merged with the reconstruction of a Neanderthal, to see what you would have looked like as an early human.  Jerry’s there now, and here’s Jerry’s photo. I’m not sure I can detect any real differences.

Jerry as a Neanderthal.

Jerry will be posting about the exhibit later (as will I, as promised).

New australopithecine described

April 8, 2010 • 11:26 am

by Greg Mayer

Lee Berger of the University of the Witwatersrand and several colleagues will be describing a new species of Australopithecus, A. sediba, from 1.78 to 1.95 million-year-old deposits in South Africa, in tomorrow’s issue of Science. The issue will also have a geological article on the find by Paul H.G.M. Dirks of James Cook University, Queensland, and colleagues, and a news item, all available now at Science‘s website (plus a podcast and video). The description is based on two partial skeletons, including a well preserved juvenile skull, most of the right arm and shoulder girdle, parts of the hip and leg, and various other bits.

Skull of juvenile Australopithecus sediba. Image from University of the Witwatersrand.

The new species has a long arm, but the pelvis and leg indicate that it was bipedal (i.e. it could both climb and walk upright). The general evolutionary conclusion the authors draw is the mosaic nature of the origin of Homo features: some Homo-like characters evolved before others, e.g. bipedality preceding cranial enlargement. They find specific features linking the new species to Homo, and posit it to be intermediate between earlier australopithecines and Homo:

The age and overall morphology of Au. sediba imply that it is most likely descended from Au. africanus, and appears more derived toward Homo than do Au. afarensis, Au. garhi, and Au. africanus.

Something I rather liked about the paper is that it is quite data rich, having tables of comparison of traits and measurements of the new find and several other fossil hominids. Such data-richness is unusual for papers in Science, which prefers short papers, with data often being relegated to electronic appendices or other papers; the Berger et al. paper is an unusual ten pages long.

The news has already reached media websites (e.g. the New York Times, the BBC and the Telegraph). Unlike the case of Darwinius masillae, however, in which premature press coverage, which included the name and its diagnostic characters, and web posting of the description, led to questions about the proper authorship and publication of the name, the authors and journalists in this case have done everything right. The news accounts are appearing coincident with the name being published (i.e. printed on paper), not prior to its publication. (The newspaper pieces linked to above are online now, but they won’t be published in the sense of the International Code of Zoological Nomenclature until tomorrow, when the scientific paper itself will be published.) There will thus be no questions about the publication of the name; the authors have made sure that, as the ICZN recommends, Australopithecus sediba is “self-evidently published within the meaning of the Code” (ICZN, Rec. 8B)

New human evolution hall at the National Museum of Natural History

March 22, 2010 • 8:59 pm

by Greg Mayer

Last Wednesday, the National Museum of Natural History (known to biologists as the USNM, the initials of its former name and still the identifying code on its specimen tags and labels) opened its newest permanent exhibit, the Hall of Human Origins.

I was at the USNM much of last week, mostly doing research in the collections and meeting with colleagues, but I always like to take a look at the exhibits, and I’d in part planned my visit to be able to catch the opening on the last day of my visit. Unfortunately, it turns out the exhibit was only open from 12-3, the rest of the day being reserved for media and VIPs, so when I went to see it a bit after 3 all I could see was one skull through a crack in a barrier. I’m planning another go at it this summer, but some of the original specimens, loaned by foreign museums for the opening, are likely to have been replaced by casts by then.

Edward Rothstein, the New York Times’ museum reviewer, whose reviews I always find interesting, did get to see it.  He gives it a mixed review. A hall worth “repeated, close viewing” suggests an exhibit rich in the diversity and number of its specimens, a characteristic of the “cabinet” style in museum exhibits, but he laments the poor execution of the computers and touch screens of the “interactive” style:

The hall bears repeated, close viewing, though children will also find amusements here, including the opportunity to come face to face with floor-level bronze models of their ancestors. But the two computer simulations at the exhibition’s end — one a simplified Sims-type game of cultural and environmental choice, the other a cartoonish vision of possible future evolutionary change — should be far more subtle. More wall text summarizing themes would have also helped: too much is left to the text of touch screens, buried inside menus of choices.

He also raises an issue that concerned me when the opening was announced last fall: that the exhibit might adopt some theological viewpoint:

There are times too when it seems as if the Smithsonian has almost gone too far in humanizing evolution, as if it were answering those who, on religious grounds, object to the evolutionary universe and its inhuman brutality. (A touch-screen F.A.Q. suggests simply that such visitors use the show to “explore new scientific findings and decide how these findings complement their ideas about the natural world.”)

At any rate, the exhibition’s focus doesn’t really give us a feel for the daring of the evolutionary vision, which is a tale not of progress but of accident, frightening in the moment, fortuitous only in retrospect.

At the exhibit website, I found the page for the Broader Social Impacts Committee. The committee consists of 14 people, all but one of whom are identified by their religion (including one “Humanist”). This is a rather odd composition and set of descriptors for a group concerned with broader social impacts– no historians, sociologists, political scientists. But as the website makes clear, the charge of the committee is to deal with religious issues. The following statement from the website, while straightforward in acknowledging the diversity of views, seems to prefer the last view (“interaction or engagement”), but its not clear to me what exactly this view entails:

There are a number of different approaches to the science-religion relationship. One approach is to see science and religion as separate domains that ask different questions focusing on separate interests in human life – for example, about the natural world in science and about God in religion. This approach depends on respecting and maintaining the distinctions but can sometimes overlook the ways in which scientific interpretations may have an effect on religious beliefs. Conflict is seen to arise when efforts are made to eliminate the separation that the first approach assumes. The strongest conflicts develop when either science or religion asserts a standard of truth to which the other must adhere or otherwise be dismissed. An alternative approach sees interaction or engagement as positive. Engagement takes many forms, including personal efforts by individuals to integrate scientific and religious understandings, statements by religious organizations that affirm and even celebrate the scientific findings, and constructive interactions between theologians and scientists seeking common ground, respect, and shared insight into how the science of human evolution contributes to an awareness of what it means to be human.

My full opinion will have to wait till I get to see the exhibit myself. One thing I’m looking forward to are the new reconstructions.  John Gurche, the renowned scientific artist, has made a set of incredibly detailed life reconstructions for the exhibit (seen here; check out the rest of his website for more paintings and sculptures), and Smithsonian Magazine has had two pieces on them.

Edward Rothstein’s final word:

But the retrospective vistas provided here are, nevertheless, compelling and illuminating. This was conceived as a permanent exhibition, meant to serve a generation of visitors, but it was also designed to be easily adaptable to the pressures of scientific advances and visitor tastes. The evolution continues.

A set of skull images released by the USNM.

(PS: On the way in to the museum that morning, Greenpeace protesters, dressed like law enforcement agents from the “Climate Crimes” unit, handed me a flyer denouncing David Koch, who contributed most of the funding for the hall (and whose name is on it). More on this angle at the Wonk Room and USA Today.)

Not all biological pseudoscience comes from creationists

August 17, 2009 • 9:36 am

by Greg Mayer

In unrelated browses through the interwebs this morning, I came across two references to some high-priced gab fest called TED, whose slogan is “Ideas worth spreading”. Both the Dish and John Hawks link to this talk at TED by Elaine Morgan of aquatic ape infamy (see Jim Moore’s website). Whoever TED is, he may want to exercise a bit more quality control when selecting speakers. John Hawks’ own take on aquatic apes is worth reading, and I particularly like his epitomization of what pseudoscience is; it’s spot on.

Is the Aquatic Ape Theory fairly described as pseudoscience? Every statement of natural causes is potentially scientific. What distinguishes science from pseudoscience is social. Pseudoscience is supported by assertions of authority, by rejection or ignorance of pertinent tests, by supporters who take on the trappings of scientific argument without accepting science’s basic rules of refutation and replication. Pseudoscience is driven by charismatic personalities who do not answer direct questions. When held by those in power, like Lysenkoism, it destroys honest scientific inquiry. When held by a minority, it pleads persecution.

I think that the Aquatic Ape Theory in 2009 fits the description. (emphasis added)

The bitterness goes way back

August 17, 2009 • 8:54 am

by Greg Mayer

In a soon to be published paper in the Royal Society’s Biology Letters (abstract only), Carles Lalueza-Fox of Universitat Pompeu Fabra ( website in Catalan!) in Barcelona and colleagues report that they have sequenced the gene TAS2R38 from a Neanderthal man (press coverage by the BBC and NY Times). The ability to sequence genes from fossil material is remarkable enough in itself, but this study has particular interest, and not just because it was done on one of our fossil relatives.  Variation in the gene they sequenced is responsible for the polymorphism in modern man for the ability to perceive bitter tastes (some people can tast bitter, some can’t). Determining the frequency of the two forms (or alleles) of the gene is a classic high school biology exercise, carried out by seeing who can taste the bitter chemical PTC.  People who have either one or two copies (humans are diploid, so most genes are present in each individual’s genome in two copies) of the taster allele can taste bitter; those with two copies of the non-taster allele cannot. Today, the two alleles are about equally frequent, so that about 25% of people have two taster alleles (i.e. they are homozygous for the taster allele), about 50% have one taster and one non-taster (they are heterozygotes), and 25% are homozygous for the non-taster allele.

The Neanderthal they sequenced was a heterozygote, and thus could taste bitter (and also [with sample of only 1, mind you] had the same allele frequencies as we do). The polymorphism thus goes back somewhere on the order of 40,000 years. But Neanderthals split from the lineage leading to modern humans on the order of 300,000 years ago, with little or no subsequent interbreeding. So the polymorphism probably goes back even further, predating the modern Homo sapiens/Neanderthal split. Although an exciting find, this is not a record for the antiquity of a modern polymorphism: some are known to predate the human/chimp split (abstract only), and that’s millions of years ago.

The evolution of laughter

June 5, 2009 • 8:55 am

Laughter appears to be a “human universal”: one of those many traits that Donald Brown, in his book Human Universals, found in every society.  Well, does that mean it is a trait that evolved in our ancestors, or did it merely appear as a cultural phenomenon early in human society, and spread to all other societies?  One bit of evidence is that children who are deaf and blind, and thus can’t see or hear other people laughing, still laugh.  This suggests (but of course does not prove) that it is an innate, genetically coded trait, though it says nothing about whether it might have been an adaptive trait.

New research just reported in Current Biology by Davila Ross et al. (see here for a short BBC summary of the work; be sure to click on the video to see a gorilla “laughing”!) suggests that laughter is at least an evolved phenomenon, for our relatives appear to show similar vocalizations when tickled, and our closer relatives show more similar vocalizations.

Davila Ross et al. tickled 3 human infants, 7 orangutas, 5 gorillas, 4 chimpanzees, 5 bonobos (pygmy chimps) and 1 siamang, recording their vocalizations. (What a great job!)  Acoustic analysis of the vocalizations produced a phylogeny, or “family tree” of their similarities.  Strikingly, the family tree based on “tickle-vocalization” analysis is congruent with the known phylogeny based on DNA analysis:

laffs

Importantly,  the authors note that several features of human laughter, like its rapid “ha ha ha” type of vocalization, and its expression only during “egressive airflow” (science-ese for “breathing out”) are found in our relatives as well.

So laughter, at least when being tickled, appears to be an evolved, innate phenomenon.  As I emphasized above, this says nothing about whether it was selected for directly, whether it was a byproduct of something else that was selected, or is simply a nonadaptive epiphenomenon.  But as I write, evolutionary psychologists are working on why evolution may have promoted laughter.  Stay tuned.

Did cooking make us human?

May 30, 2009 • 2:06 pm

Well, everybody’s looking for what propelled us from our common ancestor with chimps to the wonderful species we are today. If it’s not genes, it’s culture.  Today’s NYT discusses Richard Wrangham’s new theory (previously mentioned on this website) about how the taming of fire and its use to cook food were crucial events in making our species what it is today.  I am skeptical (I’ve seen many of these theories come and go), but still looking forward to reading Wrangham’s. new book, Catching Fire: How Cooking Made us Human.