Today's sketchbook:
KNM-ER 1802 mandible, in occlusal view. This mandible is attributed to the genus Homo, often placed in Homo habilis, although those who believe in Homo rudolfensis generally include this mandible. From the Upper Burji Member of the Koobi Fora Formation, it dates to around 1.9 million years ago.
This station has several of the key cranial specimens of Homo habilis, together with Sts 5, the representative of Australopithecus africanus. The H. habilis specimens include:
Another skull, KNM-ER 1805, is also included here. This skull may also represent H. habilis, or it may be something else.
What to do: Examine the H. habilis crania compared to A. africanus and early Homo erectus. What makes these skulls more like Homo than Australopithecus?
KNM-ER 1470 and KNM-ER 1813 are very different in size. Are they male and female of the same species, or do you think they are different species?
What is KNM-ER 1805?
The fossil record is not made up only of adults. We have abundant skeletal evidence from juvenile individuals of a broad range of ages. At this station you will find model mandibles and maxillae from human children of a range of ages. These provide a comparison for the casts at the station, each of which represents a fossil hominin specimen from Africa, between 3.6 million and 1.5 million years ago.
The mandibles represent several different species. They include:
A selection of other mandibles, including some adult mandibles of the same species, is also available. Examine these in comparison with the modern dental models. Which teeth are present in the fossil specimens? What teeth are in the process of eruption? What do they tell you about the ages of the individuals?
This past year and half I have read and studied pre-history including most of the books, dvd's, on evolution, human origins, and all related subjects. I have followed the 'time line' from Big Bang to the 21st century and returned to the 10 million year period addressing the study of man from our "beginning". To my surprise there was no clear beginning; after much study, I understand why now; after seven million years, the last hominid fossil "Toumai"then nothing but primate fossils from which
is presumed the first hominids came into being leading to the evolution of some 17-20 species thru four groups. It appears
that from 7 mya to 10 mya is the famous "missing link" or gap with no fossil evidence of the "split" or diversion therefrom is
the contentious question and debate.It is very impressive what Paleoanthropology and related sciences have discovered of our origins and the progressive
patterns of human development that explains so much of our existence for some 10 million years and estimated 108
billion that have come and gone. Yet! the story of 'man' is incomplete without an explaination of how, within the science of
molecular evolution, the genetic codes and finally through sexual reproduction from our closest relatives..... the primates.After all the reading and research I have done, I am convinced that you and the science of Paleoanthropology work daily
to find the answer to the first hominids, there is nothing you would desire more that answer this question. My question:
Is there sufficient knowledge acquired to date that a story or explanation can be published declaring a clear beginning
picture that will give us a new 21st century Genesis?? It appears to me that we now have enough molecular and fossil
evidence to achieve the task! Of course including related sciences, climate, ecology etc. What do you think?
Thank you so much for your kind words!
I am maybe less hopeful than you, because I see the great difficulty of the task. We understand much about the time when our ancestors first diverged from the apes but our fossil record from that time has really only just begun. We will more quickly have an idea of how our genes changed from that time, but genetics is a bit like driving on the road and taking a note of each town you pass, then tossing all the notes into a hat and drawing them randomly. We do not know which genetic changes were the first, and therefore we have difficulty seeing why the events happened at the beginning.
My lab is directing our attention to the origin of Homo, around two million years ago. Here, the fossil record also is starting to fill in, but we additionally have the ability to determine which genetic changes might have happened at around the same time. Ancient DNA evidence has totally transformed our ability to study this time period. When we can understand this kind of event from the perspectives you mention, then I think we will be ready to tackle the origin of the hominins!
These are a few of the questions that I think are essential to understand our aims with the project and how we expect it will unfold. The future depends on what we hear from people with their ideas about how to analyze this unique evidence. I'll be updating this FAQ as we learn more about the samples. This is an open science project, and we'll be reporting on some results as they occur. But it all depends on people's participation.
If you've arrived at this page from outside the site, here's a link to the main project headquarters.
When I was in South Africa in July, Lee Berger gave me an extraordinary overview of the discoveries from the new Malapa site. Embedded in the breccia that surrounded the cranial remains of MH1 and MH 2 are some relatively small, thin layers that visually appear to be organic (relative to the surrounding matrix). Under a light microscope look like they could be mineralized or preserved soft tissue. They do not appear to be skin impressions within the matrix, they appear to be thin layers that are a different substance from the surrounding matrix.
Naturally these are incredibly interesting. But it is not obvious what will be the best way to establish what they are, and what we can learn from them.
Lee suggested that this would be an ideal test case to see if open science can help solve a problem in paleoanthropology. We want to reach the people with the best ideas and ability to test hypotheses about these objects, and we don't know in advance where the answers will come from. That's the nature of the project: finding the right people and making the science happen.
We want the best suggestions about how to evaluate this unique evidence and how it can test hypotheses about human evolution. We're reading all the suggestions sent to skin@johnhawks.net.
We're especially keen to make contact with people who have the ability to make their suggestions happen. Some people out there have the knowledge to apply highly specialized analytical methods to samples like this. We want people like that to get involved with this project.
Some people out there may have comparative samples that will be key to interpreting this evidence. How can tissue be preserved in a context where breccia is forming? Was there natural mummification or some kind of anoxic environment? To answer those questions, we need people who study the response of tissue to those contexts and who know the right samples to examine.
Berger's team working on the Malapa hominins have access to much of the best technology. Micro-CT, microscopy, virtual dissection, chemical analysis, any of these things and more can be brought to bear.
There's a lot more to this project than simply verifying (or refuting) that this stuff is soft tissue evidence. We need to know how it formed. If it's not soft tissue, we want to identify what it is, because there will almost certainly be more of it as the site is excavated and more specimens are prepared. If it is soft tissue, we need to know how it may have been changed as it was preserved, whether through drying, soaking in anoxic conditions, mineralization, or some combination of processes.
We think the process of finding this out is even more exciting than knowing the result. We hope many of you see it the same way.
If you write to us, you can expect that we may make your suggestion part of the website. This is an open project, and while we will be posting selectively, we will be sharing information as it progresses.
We want to do the science right. We hope many people out there share this goal. It's a tremendous chance for people who don't normally operate within paleoanthropology to help us discover something fundamentally new about our evolution.
People who perform analyses or contribute samples as part of this project happen will be full participants in the science and coauthors of any resulting publications. We want people to work together on this, and we think the best science will result from bringing together the best ideas and comparisons.
That depends on what great ideas we hear from people. Lee's team will be carrying out analyses on these samples.
Rachelle Keeling is coordinating the study, doing the research on what should be done, and what it will tell us about the samples. She and I will be reviewing the e-mails that the project receives, and will try to determine which approaches are feasible, and which order they should be carried out.
As you send in ideas about what should be done, the more detail you can include about the analytical methods you can provide, the better. How much material (if any) does the method require? What hypotheses can the method test, or what information can it provide about the samples? How much time and preparation is required?
If you have comparative samples that may be useful, what kinds of observations can you make on them? Can you point to references that have also used these samples?
In other words, we want a bit of a plan if you can provide it. If you need more information from us to see if it's feasible, let us know -- we may be able to answer it, or have some team members carry out steps in advance.
The project will be carried out over the next year, so the sooner we hear from you, the better!
Malapa is a cave site outside Johannesburg, South Africa, in the area where many other sites preserving remains of early hominins have been found. I have a Malapa page that gives a short introduction and links to many stories here about the fossils found at the site. I visited the site in July, 2011, and posted a narrative of the visit ("A visit to Malapa") that gives a good overview and several photos of the general area.
Two of the most complete hominin skeletons ever described, both dating to 2 million years ago, have been discovered and described at the site. The site additionally includes further fossil materials that are still undergoing preparation and study. It is one of the most important fossil discoveries ever made in paleoanthropology, and will continue to produce new evidence about our origins for many years to come.
So far, the team at Wits has been working on breccia blocks recovered from the surface at Malapa. There has been no excavation yet at the site. The possible soft tissue evidence was discovered during the course of scanning and preparing these breccia blocks.
The blocks are packed with bones. Many recognizable bones jut from the surfaces of the breccia, from antelopes, carnivores, small baboons and hominins. In several cases, hominin bones were recognizable at the surface, and these blocks were CT-scanned very early in the process of study and preparation. Scanning gives the preparators knowledge of what lies beneath their drill bits. In some cases, the best course of action is to leave the bones embedded within the breccia matrix, for further study by micro-CT.
Initial CT scan of the MH1 cranium embedded in matrix block.
In the initial CT-scanning of the MH1 cranium, team members noticed an area where the matrix surrounding the skull appeared irregular. As they prepared this out, it became clear that the breccia itself had pulled away from the cranium across a small region, and the breccia had a thin layer of material at its surface there. This is not the outer table of the bone (which is intact in the corresponding area), nor is it apparently an impression of the bone.
Photo of breccia block including MH1 cervical vertebra (top). The smooth area, center, is a thin layer of candidate soft tissue on the surface the breccia.
An additional section of possible soft tissue emerged as the female MH 2 mandible was prepared.
Upon magnification, these pieces do appear to have a structure. As yet, no dissection or further sampling has been attempted. The team has no committed opinion about what these represent or how they were formed, other than that they do not appear to be simple impressions in the surface of the breccia. Disproving that they represent soft tissue may be just as interesting as demonstrating it, because either way we will discover important facts about the preservation and formation processes of this unique site.
Like other South African cave sites, the Malapa fossil hominins were preserved within a breccia, a cemented stone material packed with fossils, rock fragments, and other material. The Malapa breccia represents a remarkable snapshot of time, when hominins and other animals fell into a "death trap" and their complete skeletons were preserved.
It is clear that Malapa preserves an extraordinary density of hominin remains, with nearly complete skeletons and articulated parts. These skeletons do not appear to have been disturbed after the bodies entered the site. Some plant and insect remains are preserved in the breccia as well.
Beyond this, any explanation so far is speculative. If there was water in the site, which seems likely, it may have included an anoxic layer that preserved some of this material. A major goal of the project will be testing different hypotheses about the preservation environment of these fossils, to try to explain what these substances may be.
:)
I've enabled the search function for the site, which you'll find at top right on each page of the site. The search index is still rebuilding, and as I write this has only indexed 4% of the site. That brings it up to late 2007, and it's interesting to go back through the history of paleoanthropology that way.
For example, I ran across my comments ("Is a lack of fossils the problem with early Homo?") on a John Noble Wilford piece from four years ago. Seems very timely in many ways. For example, the paucity of the fossil record of Homo before 1.6 million years ago was a major feature of the article. I directed my attention to the supposed "gap" between 3 and 2 million years ago:
[W]e actually have quite a lot of fossils from this time period. The entire South African A. africanus fossil record, with the exception of a few early specimens like STW 573, come from this "gap." A fairly extensive record of the appearance and evolution of early robust australopithecines comes from this time period in East Africa.
And, here and there, a few specimens look Homo-like. Wilford's article discusses AL 666-1. To this we can add the Uraha mandible, Omo 75-14, an additional series of teeth from Omo, and possibly the Bouri BOU-VP 35/1 skeleton.
Properly considered, the rarity of early Homo in these contexts is not a problem; it is information.
Of course, dates have changed. We now have good dates for Dmanisi, which make those fossils the earliest well-attested Homo erectus sample at 1.8 million years. STW 573 now looks late, not early. But the fact remains that people were looking for pure representatives of Homo in the fragments instead of exploring morphological diversity within the large and fairly complete samples at hand.
National Geographic has posted text from Josh Fischman's August article about Australopithecus sediba: "Malapa fossils".
This raises the possibility, says Berger, that all the hominins—at least four are now known from the site—died weeks or even days apart, and therefore may have known each other in life. The rapid burial also caused their flesh to take longer to decompose, packaging the skeletons in death as they were arranged in life, right down to tiny bones of the hands and feet. Indeed, the rapid entombment may have preserved some of the skin itself, on top of the boy's skull and on the woman's jaw near the chin—something never before seen in a hominin fossil.
It's pretty cool to be here with the fossils and the people involved in the story right now. The story nicely features many members of the extensive team involved in the preparation and analysis -- a process that has unfolded so far in less than three years from the discovery of the site.
The article emphasizes what may be the central scientific problem posed by A. sediba: what it means for early Homo. As I wrote last month, the origin of Homo is by far the most interesting problem in human evolution right now.
Dennis Etler has been going great guns on his blog, Sinanthropus.
Last week's article claiming cutmarks on A. afarensis-aged fauna from Dikika (Australopithecus afarensis used stone tools) got Dennis to write a provocative post: "Its time to sink the genus Australopithecus redux."
Either A. afarensis should be revised to H. afarensis or the possibility must be entertained that the Woranso-Mille individual and the maker of the stone tool cut marks at Dikika represent a new previously unknown species of Homo (perhaps H. antiquus Ferguson 1984) that lived contemporaneously with A. afarensis.
He mentions the relevance of the Woranso-Mille skeleton (which I haven't yet gotten to here) and A. sediba for this conclusion. Etler's earlier post, "It's time to sink the genus Australopithecus" goes into more detail on these remains.
To me, the key question is whether Homo as we understand it now (including H. habilis) is polyphyletic. One way to escape this question is to narrow our genus, placing H. habilis and its ilk into Australopithecus. But Australopithecus defined broadly in this way is almost certainly paraphyletic. And that's without considering the issue of robust australopithecines. I can see why one might follow Ernst Mayr and stick them all in Homo.
I have to credit a reader for that headline, and for forwarding the paper. It's another case of the infamous PNAS release policy. The press that came from the paper's announcement preceded the paper's availability in this case by a week. That approaches the case where a Hollywood studio won't screen a movie for reviewers before it's released. That means no reviews, which in the case of movies can only mean one thing. It's bad.
Scientific papers fortunately don't suffer from this shortfall -- the quality of the paper seems more or less unrelated to the release policy of the journal. In this case, the press went with a story that is interesting, but not necessarily that important in the scheme of things. And I don't get to write about it until two weeks after the news stories hit the presses.
David Braun and colleagues report on the fauna at locality FwJj20 of Koobi Fora, Kenya. The archaeological remains here, including stone tools and fauna, date back to 1.95 million years. It's an interesting time because of what may have been going on with hominin anatomical evolution, but does it represent anything new in behavioral evolution?
The authors point out that there are archaeological sites that are much older, going back to 2.6 million years. Some of those earlier localities -- notably, the earliest, Gona OGS 6 and OGS 7 localities -- have hundreds of stone artifacts combined with fauna and hominin-modified bones. FwJj20 stands out in combining a very large number of stone artifacts (2633) with a high proportion of hominin-modified bones (5.9 percent of 405 faunal specimens). Even in later deposits such as Olduvai Gorge that have a high number of localities with some stone tools, it is rare to find localities with evidence of butchery of many animals. Those are the kinds of archaeological debris that would be expected of a real focus of hominin behavior. So every additional site like this adds substantially to our knowledge of hominin behavior at the dawn of hunting and gathering.
Here, one interesting aspect of the faunal exploitation is the small amount of surface modification consistent with bone-smashing. The authors suggest that the site had little marrow extraction than expected based on experimental replication of butchery. There is very little evidence for carnivore activity at the site, and both bones and faunal remains are clustered within a small vertical horizon of around 6 inches in thickness. The presence of small flakes and bone fragments helps to substantiate that the site did not accumulate under the influence of high-velocity water flow, and that it represents a primary activity locus for the hominins who left the tools there.
The faunal assemblage is interesting for the relatively high proportion of aquatic animals preserved, including both turtle and crocodile bone specimens with cut marks, and some fish bones. This is the part of the paper emphasized in the press that described the site, and the paper gives a good summary of the aquatic proportion of the fauna, including the evidence that the animals were actually butchered by the hominins.
The skeletal representation of fish bones [over-abundance of cranial fragments: 64% of fish NISP (28)] and turtle/tortoise bones [over-abundance of carapace and plastron fragments: 90% of turtle/tortoise NISP (29)] corresponds to ethnographic and archaeological distributions associated with hominin foraging. The number and taxonomic diversity of hominin-modified bones imply that hominins used the FwJj20 locality for the acquisition of meat from several different carcasses of terrestrial and aquatic animals as well as marrow from mammalian bones. This provides strong evidence of a diverse animal component in the diets of hominins before the appearance of H. ergaster/erectus (Braun et al. 2010:10004).
But....I think that the relevance of the aquatic animals has been exaggerated. According to the MNI (minimum number of individuals) table in the paper, the turtle and crocodile bones may represent one single turtle and one crocodile. The number of fish bones is also very small -- only 15 total, and the authors do not provide an MNI for fish. Compare these small numbers to a minimum of 11 hippopotamus individuals represented by in situ bone elements, and 17 bovids. One turtle. Seventeen bovids.
MNI is not the best indicator of dietary importance -- for mammals, it is heavily influenced by mandibles and teeth. Humans may drag mandibles back to a central place as part of the head, even if they eat the rest of the animal elsewhere. Being highly diagnostic, we can work out easily when there were lots of individuals from a mandible -- not so for broken turtle carapace pieces. But it's not very meaningful to count every crocodile bone, either. The site really does not provide any evidence that reptiles and fish simply made up a large fraction of the meat consumed there.
From my perspective, I think that's just fine. Aquatic animals aren't important because of their sheer numbers, but because they tell us about the flexibility of foraging behavior. Living hunter-gatherers eat turtles and reptiles when they can, and because they are usually small food packages, they often eat them where they find them instead of returning to a base camp first. Hunter-gatherers are flexible in what they eat and where they eat it. FwJj20 is showing at least a substantial taxonomic flexibility in the meat-eating of early Oldowan hunters.
Croc, turtle and fish remains also document that the Oldowan-makers were actively foraging in and around river or lake margins. That may not be earth-shaking, since we are, after all, talking about a water-dependent primate in a hot climate. But sometimes the importance of an archaeological discovery is that it strikes a "couldn't have done it" from the record.
Still, this really isn't a case where anybody could credibly maintain that early hominins were excluded from foraging on lake or river margins. Just last year I discussed two archaeological sites that give evidence for human exploitation of aquatic resources in the Early and Middle Pleistocene. At Trinil, Java, it seems clear that people were exploiting molluscs ("The shells of Trinil"), and the somewhat later Gesher Benot Ya'aqov site in Israel has evidence of systematic fish and crab exploitation ("The fishy spaces of the Middle Pleistocene"). The possible exploitation of papyrus by A. boisei also would show a mastery of shoreline habitats by hominins. It's hard to argue that the threat of the water was lower for robust australopithecines than for Homo.
Finding such repeated evidence of aquatic resource use, extending back near the dawn of stone tool manufacture, ought to prove one thing: The fatty acids in aquatic meat were not the cause of the expansion of brain size in Homo erectus.
Oh, I know, the news stories all said exactly the opposite, claiming that the fatty acids were essential to brain growth, and that this shows that stone tools were important to getting this essential nutrient. Hey, Braun and colleagues started it -- they wrote it right in the last sentences of the paper:
In addition, although animal tissues provide nutrient-rich fuel for a growing brain, aquatic resources (e.g., fish, crocodiles, turtles) are especially rich sources of the long-chain polyunsaturated fatty acids and docosahexaenoic acid that are so critical to human brain growth (2). Therefore, the incorporation of diverse animals, especially those in the lacustrine food chain, provided critical nutritional components to the diets of hominins before the appearance of H. ergaster/erectus that could have fueled the evolution of larger brains in late Pliocene hominins (Braun et al. 2010:10005).
But "fueled" is a metaphor, not a valid evolutionary concept.
I accept that reptile and fish meat may be nutritionally desirable. The question is whether they caused the increase in brain size associated with Homo. One way to read that hypothesis is as Lamarckism, which is simply wrong (Larry Moran has commented on that topic). I don't think that any paleoanthropologists are seriously Lamarckist, but some need to be more careful how they describe the relationship of fitness and diet.
Let me construct a version of the hypothesis consistent with evolutionary biology. Suppose that other factors -- social competition, technological requirements -- induced selection for cognitive skills in early Homo. The response of the population to this selection may have been impeded by selection in favor of smaller brains and/or shorter life histories. That is to say, directional selection on cognition may have been impossible because of stabilizing selection on brain growth. Now diet changes might become relevant, by relaxing the stabilizing selection on brain growth. This scenario might predict an increase in the size of the brain when people began to consistently supply themselves or their children with the right nutrition.
Understand that I don't subscribe to this hypothesis. We have much to learn about what the "right" nutrition might be.
But the hypothesis is testable. The archaeology now suggests that significant meat consumption preceded the expansion of the brain by a half million years or more, and that fish and reptile meat made up a hunter-gatherer-like part of early hominin meat consumption from the start.
Now it could be that later increases in diet quality -- for example, by increasing the total amount of meat, or decreasing nutritional unpredictability -- are what actually caused (or allowed directional selection on) the increase in brain size. That change would be a different hypothesis, however -- the hypothesis that selection against larger brains was relaxed by behavioral innovation. Fish fat could be a correlate of behavioral change in this hypothesiss, but it would not be the cause.
Braun DR, Harris JWK, Levin NE, McCoy JT, Herries AIR, Bamford MK, Bishop LC, Richmond BG, Kibunjia M. 2010. Early hominin diet included diverse terrestrial and aquatic animals 1.95 Ma in East Turkana, Kenya. Proc Nat Acad Sci USA 107:10002-10007. doi:10.1073/pnas.1002181107
