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paleoanthropology, genetics and evolution

Photo Credit: From the catwalk at Sterkfontein. John Hawks CC-BY-NC-ND

First Peoples: Asia, and Australia

First Peoples continues tonight on PBS, with two episodes that focus on the dispersal of modern humans into Asia and Australia.

The Asia episode includes archaeological work at Tam Pa Ling, Laos, and goes to the Arabian peninsula with Jeff Rose to track the earliest archaeological evidence of African contacts there. The episode introduces the mysterious Denisovans and talks about the importance of this population mixture to present-day populations.

The Australia episode begins with the Lake Mungo skeletal remains, which similar to the Kennewick skeleton in the U.S. were the subject of conflict between government and indigenous groups. The film visits several sites of heritage significance in Australia, guided by the aboriginal caretakers. And the narrative focuses on the long habitation of the Australian continent through periods of climate change, and the cultural innovations that made it possible to maintain populations within the harsh conditions of the Australian interior.

Coming: 'First Peoples' on PBS

This month, PBS in the United States will be premiering a new five-part series on the origins and spread of modern humans around the world, called First Peoples. The first two episodes, featuring the spread of people into the Americas and the initial origin of modern humans in Africa, will be shown on most PBS stations on the evening of Wednesday, June 24. Later episodes cover the entry of modern humans into Asia and Europe, where they mixed with Neandertals and Denisovans, and the appearance of ancient peoples in Australia.

I’m very proud to appear in all five episodes, where I help to provide a common thread discussing the success of modern humans and the importance of population mixture in our origins. I’m also very pleased with the overall balance of the series. Each episode covers new archaeological discoveries, often from sites that have only been known for a few years, and in several cases discussing unpublished work. Going into the field to cover these archaeological sites adds a real beauty to the series. Meanwhile in each episode new genetic findings come into the story, especially those from ancient DNA that have added so much to our understanding of the interaction of ancient people.

PBS has set up a great website for the series, with background information and clips. Here’s a link to a clip where I describe the importance of population connections across Africa during the early MSA: “The Secret to Our Success - Connectivity”.

I’ll be following up with more information about each of the episodes as the air date approaches.


From Plagues and Peoples by William H. McNeill, a passage synthesizing the role of endemic parasites in weakening entire populations:

Whatever the ancient distribution of schistosomiasis and similar infections may have been, one can be sure that wherever they became widespread they tended to create a listless and debilitated peasantry, handicapped both for sustained work in the fields and digging irrigation channels, and for the no less muscularly demanding task of resisting military attack or throwing off alien political domination and economic exploitation. Lassitude and chronic malaise, in other words, of the kind induced by blood fluke and similar parasitic infections, conduces to successful invasion by the only kind of large- bodied predators human beings have to fear: their own kind, armed and organized for war and conquest. Although historians are unaccustomed to thinking of state building, tax collection, and booty raids in such a context, this sort of mutual support between micro- and macroparasitism is, assuredly, a normal ecological phenomenon.

Alex Tabarrok writes at Marginal Revolution: “Should we care if the human race goes extinct?”

Why should we be worried about the end of the human race? Oh sure, there are some Terminator like scenarios in which many future-people die in horrible ways and I’d feel good if we avoided those scenarios. The more likely scenario, however, is a glide path to extinction in which most people adopt a variety of bionic and germ-line modifications that over-time evolve them into post-human cyborgs. A few holdouts to the old ways would remain but birth rates would be low and the non-adapted would be regarded as quaint, as we regard the Amish today. Eventually the last humans would go extinct and 46andMe customers would kid each other over how much of their DNA was of the primitive kind while holo-commercials advertised products “so easy a homo sapiens could do it”. I see nothing objectionable in this scenario.

Regarding others as quaint is a cultural armament of a particular local median. The Amish population in the U.S. has a doubling time on the order of 22 years and in recent years around 85% of those born into Amish communities have remained in those communities as adults. Cultural forces are strongest at the local median, and in 21st century nation-states, the difference between local and global is defined by religious and ethnic boundaries.

Why do male bonobos have such low body fat?

I can’t be the only one surprised at how little body fat male bonobos have. A study of bonobo dissections by Adrienne Zihlman and Debra Bolter (2015) included data from six female and seven male bonobos collected over many years. The females had very low body fat percentages, with the highest value only 8.6% and three of the six females under 1.2%. But the males were the interesting story, with no male among the seven measured as high as 0.01% body fat.

As Zihlman and Bolter explain, these are minimum estimates, since the necropsied bonobos did not necessarily include fat included in the viscera or near internal organs, and fat that could not be dissected as separate chunks was not weighed separately. But subcutaneous fat and other small adipose areas are included in this estimate, and comparable values for male humans are upward of 20%. They comment on the surprising finding:

The negligible measurable fat in all seven P. paniscus males was unexpected, overriding captivity, age, and body mass. Among wild chimpanzees, there is little indication of an ability to mobilize fat stores during times of caloric restriction, a key adaptive feature found in orangutans and possibly to a lesser degree in gorillas (24, 52, 53). Without selection pressure for storage fat, and with over half of body mass in muscle, the male P. paniscus does not easily accumulate body fat, even under optimal circumstances of captivity. Remarkably, none of the males and females manifested detrimental health as a consequence of having little fat, in stark contrast to H. sapiens.

I was interested in whether this is a bonobo-specific phenomenon. Zihlman and McFarland (2000) dissected four captive gorillas and found both males and females to have substantial body fat percentages, ranging from 19.4% to 44%. Wolfgang Dittus (2013) reported on the body fat distribution of wild toque macaques, finding that they had approximately 2.1% body fat, more than 80% carried within the viscera and other intra-abdominal areas and only a small amount subcutaneously. Males and females did not differ on average.

Interestingly, a study of zoo chimpanzees by Elaine Videan and colleagues (2007) found that no male chimpanzees could be categorized as overweight, and that they differed from females in skinfold and triglyceride levels. From that paper:

The range of serum triglyceride and glucose levels for male chimpanzees was considerably smaller than that of female chimpanzees (Figs. 2, 3). In fact, none of the male chimpanzees in this study had serum triglyceride levels above 150mg/dl (< 150 mg/dl 5 normal human reference range) despite having BMIs that ranged as high as 149.5. In addition, most of the mean skinfold measurements for male chimpanzees were half that of the female values (Table 1). We hypothesize that the high BMIs observed in many of the male chimpanzees in this study reflects high lean body mass (i.e., muscle mass) rather than high body fat.

So there does seem to be something about male chimpanzees and bonobos.

Lest you think that human body fat is just a post-agricultural phenomenon, Herman Pontzer and colleagues (2012) reported on body composition in the Hadza population of Tanzania, who live a hunter-gatherer lifestyle. In that population, women range from 12.4 to 27.7 percent body fat, and men range from 7.4 to 23.1 percent body fat. This is much less than in Westernized societies and is also less than in subsistence farmers, although the difference there is not so great as most might assume. There is a story of body fat in human evolution, and certainly the high body fat composition of humans—even human foragers—contrasts with most wild primate populations. It may be that bonobos and chimpanzees are not the appropriate comparison because of their own distinctive evolutionary trajectories.

References

Pontzer H, Raichlen DA, Wood BM, Mabulla AZP, Racette SB, Marlowe FW (2012) Hunter-Gatherer Energetics and Human Obesity. PLoS ONE 7(7): e40503. doi:10.1371/journal.pone.0040503

Dittus WP (2013). Arboreal adaptations of body fat in wild toque macaques (Macaca sinica) and the evolution of adiposity in primates. American journal of physical anthropology, 152(3), 333-344. doi:10.1002/ajpa.22351

Videan, E. N., Fritz, J., & Murphy, J. (2007). Development of guidelines for assessing obesity in captive chimpanzees (Pan troglodytes). Zoo biology, 26(2), 93-104.

Zihlman AL, Bolter DR (2015). Body composition in Pan paniscus compared with Homo sapiens has implications for changes during human evolution. Proceedings of the National Academy of Sciences, 201505071. doi:10.1073/pnas.1505071112

Zihlman, A. L., & McFarland, R. K. (2000). Body mass in lowland gorillas: a quantitative analysis. American Journal of Physical Anthropology, 113(1), 61-78.

On the importance of saying you're wrong

Lior Pachter writes this week on his blog about the reactions and commentary around a post-publication peer review exercise he conducted on a 11-year-old paper. In the process, he reflects on some of the problems that attend the frank public conversation about weaknesses and strengths of scientific work: “I was wrong”.

Earlier in this post I admitted to being wrong. I have been wrong many times. Even though I’ve admitted some of my mistakes on this blog and elsewhere in talks, I would like to joke that I’m not going to make it easy for you to find other flaws in my work. That would be a terrible mistake. Saying “I was wrong” is important for science and essential for scientists. Without it people lose trust in both.
I have been particularly concerned with a lack of “I was wrong” in genomics. Unfortunately, there is a culture that has developed among “leaders” in the field where the three words admitting error or wrongdoing are taboo.

He discusses recent examples including the snafu induced by the ENCODE Consortium’s insistence that 80% of the human genome is “functional”. He goes on to discuss the importance of public critique of the professional behavior of scientists, with a quote that deserves sharing:

I therefore believe it is not only acceptable but imperative to critique the professional behavior of persons who are scientists. I also think that doing so will help eliminate the problematic devil–saint dichotomy that persists with the current system. Having developed a culture in which personal criticism is outlawed in scientific conversations while only science is fair fodder for public discourse, we now have a situation where scientists are all presumed to be living Gods, or else serious criminals to be outlawed and banished from the scientific community. Acknowledging that there ought to be a grey zone, and developing a healthy culture where critique of all aspects of science and scientists is possible and encouraged would relieve a lot of pressure within the current system. It would also be more fair and just.

The study he describes in the post, and the attendant experiment in examining p-values for certain kinds of genomic questions, are interesting and worth reading. As many have pointed out, it is unfortunate that so few pieces of scientific work can achieve such broad interest in the form of public discussion.

I also think it’s worth sharing an excerpt from a comment at the site from Claudiu Bandea:

“The traditional, closed peer-review system and the conventional ‘civility’ associated with the science enterprise, have allowed, if not encouraged, people to prosper by misrepresenting facts and overhyping their work (at the expense of science and their colleagues), without the *fear* of open and explicit exposure.
And, unfortunately, in order to be able to compete in such a corrupt environment, many of their peers had little choice but to lower their ethical and scientific standards and join this unproductive and reckless competition; and, by doing so, all of them (even the most reckless ones, who often display embarrassing CVs inflated with pompous titles and rewards) have become victims of the system.

When I hear people talk about being unwilling to engage in debate except in the “proper” peer-reviewed forums, this is exactly what I assume they mean.


Recommended: a post by history of science student Paige Madison on the forgotten George Busk: “On Being Remembered: Huxley, Busk, & Scientific Friendships”.

MSA from Karungu, Kenya and the patchy landscape of Late Pleistocene Africa

J. Tyler Faith and colleagues report in the current Journal of Human Evolution on their work understanding the context of the Middle Stone Age archaeological deposits from Karungu, Kenya. Karungu is an area on the eastern shore of Lake Victoria, with many Pleistocene exposures that contian archaeological evidence. Faith and colleagues set out to reinvestigate archaeological sites that were first explored during the 1930s and then later in the 1980s, to hopefully determine where they fit in time and context of other East African MSA occurrences.

The article presents paleoenvironmental data including the faunal list, species abundances of different faunal elements, and some stable isotope data on the fauna, all of which reflect an arid grassland paleoenvironment. That’s a contrast to today’s local environment in the Lake Victoria basin, which is woodier, including a range of bushlands and forests. The team were able to narrow down the timing of the archaeological deposits to some extent, placing them between approximately 92,000 and 45,000 years ago, the later part of the MSA in this part of Africa.

There are two really interesting aspects to Faith and colleagues’ presentation of the data, that together add up to a hypothesis about the movement and contacts of people during late MSA times in eastern Africa. First is a series of observations that suggest that Lake Victoria was much reduced during the time of the Karungu deposits, with lots of herbivores adapted to an arid grassland environment. Second is a statistical link between the archaeological assemblages at Karungu and other sites further to the north. When combined, Faith and colleagues argue that these data suggest north-to-south dispersal of archaeological patterns along with the spread of arid grasslands during the Late Pleistocene. The timing is very interesting: At or shortly after modern humans had established populations in West Asia, some populations of MSA people may have been expanding to the south through East Africa.

Paleoenvironment

The Karungu sites present abundant evidence of now-extinct grassland-adapted species. These include extinct relatives of modern blesbok, impala, wildebeest and oryx. As Faith and colleagues discuss, several of these species were thought to have become extinct more than 400,000 years earlier:

Previous research on late Quaternary fossil assemblages from East Africa indicated that—with a few minor exceptions (Marean and Gifford-Gonzalez, 1991 and Marean, 1992)—an essentially modern faunal community was in place by ∼400 ka (Potts et al., 1988 and Potts and Deino, 1995). However, the emerging evidence from the Lake Victoria Basin reveals the long-term survival of archaic lineages thought to have disappeared >500 ka, including Kolpochoerus, together with the many extinct bovids characterized by large body mass or exceptional hypsodonty, including S. antiquus, Megalotragus, D. hypsodon, R. atopocranion, and Aepyceros sp. nov. ( Faith et al., 2011, Faith et al., 2012, Faith et al., 2014 and Faith, 2014). Of these, only S. antiquus and D. hypsodon are known from other Late Pleistocene faunal assemblages in East Africa ( Marean and Gifford-Gonzalez, 1991, Marean, 1992, Faith et al., 2012 and Rowan et al., 2015).

In addition to these extinct species, the faunal community is further dominated by grassland species that still exist today, including some that have geographic ranges fairly far from the Lake Victoria region. They further note that Mfangano Island has Pleistocene fauna that may date to 80,000 years ago that similarly suggest an open grassland and a connection to the mainland, which would have required at least a 25 m reduction in the lake level. Put together, these pieces of evidence suggest that sometime between 100,000 and 50,000 years ago, the Lake Victoria region was a grassland mecca hosting a mix of species no longer found anywhere in Africa.

This raises a question: Was the Lake Victoria area a refuge for these grassland species into the later Middle and Late Pleistocene? Or have the extinct species been missed at other sites because of small faunal samples? Faith and colleagues do not exclude either of these possibilities. Considering the evidence for substantial fluctuations in African rainfall and lake levels, it seems unlikely to me that the Lake Victoria region was a long-term refugium; those animals must have been living somewhere else during Pleistocene times that rainfall and lake levels were higher.

It is a sobering message that the sampling of African paleoecology during the Middle Pleistocene is so sparse that we have missed many large herbivores in the period following 500,000 years ago. Even more sobering is the implication that previous paleoecologists and archaeologists have promoted the idea of a large-scale faunal turnover which in reality merely marks local environments and sparse sampling.

MSA archaeology

Ancient humans seem to have been effective at dispersing within this arid grassland. Faith and colleagues compared the archaeological assemblage from Karungu with other sites across eastern Africa, keeping track of sites both above 5 degrees North latitude and at the equator and further south. They find that these sites contrast in the pattern of assemblage composition in a way that reflects latitude, with the more northern sites contrasting with southern sites. The Lake Victoria sites, Karungu and Rusinga, are outliers in their similarity to sites further to the north.

Our analysis of the Late Pleistocene MSA record from East Africa reveals previously unrecognized north–south variation in assemblage composition (Fig. 10), paralleling the geographic patterns observed in the genetic records of ungulates (Lorenzen et al., 2012) and other vertebrates (Dehghani et al., 2008 and Miller et al., 2011). We interpret these differences, reflecting to some extent the variable occurrence of bipolar cores, anvils, large bifaces, and Levallois points or point cores (Table 5), as potentially indicating the development of regionally distinct behavioral patterns during past episodes of population fragmentation, for which the equatorial dispersal barrier is a probable driver. In agreement with Cowling et al. (2008), this implies that the potential for north–south human dispersals across East Africa would have been maximized during climate phases that promoted an expansion of grassland cover.
The grassland-associated MSA assemblages from Karungu and nearby Rusinga Island are characterized by a combination of artifact types that is more typical of sites found further north of the equator. This may reflect the southward dispersal of northern behavioral repertoires during a grassy phase that facilitated dispersals, including those dispersals of northern ungulates such as Grevy's zebra and white rhinoceros (Fig. 8).

The “equatorial dispersal barrier” here refers to the forest corridor that expands across the African equatorial region during wetter periods of time. Although this forest serves as a major dispersal corridor for species that depend upon it, including the great apes, it has been conceived as a barrier for grassland-adapted species.

Faith and colleagues help to show that different patterns of material culture existed within an area where they had not previously been noted in this way. In other parts of Africa, long-term cultural differences during the MSA have long been apparent. These are the traces of ancient populations that were to some extent biologically differentiated, but of whom we have very little evidence from physical appearance. We have some evidence from the genetics of living Africans that highly-differentiated populations once coexisted, and later mixed. It is not evident from genetics whether those populations existed over large parts of the continent or whether they were more localized. Nor is it apparent how many such populations there may have been.

It is therefore very significant that Faith and colleagues are able to show long-distance connections across the grassland environment of East Africa. The connections between the Lake Victoria sites and other MSA sites to the north are one piece of evidence for such connections. Another is the presence of exotic obsidian in the archaeological assemblage from Karungu, which they show is most likely to have come from the Rift Valley 250 km to the east. Another suggestion of contacts with the Rift Valley comes from a third outlier in the north-south dichotomy of archaeological pattern, the site of Prolonged Drift, which lies near Lake Nakuru in the Kenyan rift. Humans were able to exploit a changing climate, even as it became more arid. They maintained long-distance trade and exchange of ideas across distances of hundreds of kilometers.

Maybe this population was mixing more with people who had formerly been more isolated and differentiated from each other.

Or maybe this apparent expansion of northern technical patterns merely represents one layer among a series of flows of populations through the region during the Late Pleistocene. I am hesitant to accept the notion of an “equatorial dispersal barrier” as applied to human populations generally. Even as applied to herbivores, the concept has problems, as the interruption in gene flow caused by spreading forests is relatively short compared to the time that grazing species have existed. With humans, the problem is that dispersal is not limited to grasslands. Some human cultures elsewhere seem to have been very effective at dispersing along ecotones, edge habitats between savanna and woodland.

As an example, today’s central African Pygmy peoples descend from ancient populations that had already become established by 50,000 years ago. Many have speculated that the ancestors of today’s Pygmy peoples, established by 50,000 years ago, were forest-adapted people from their earliest times. If so, the habitation of some of the forested parts of central Africa may have been well underway by the time of the Karungu sites. A continuous forest may be a barrier to the dispersal of people with a grassland cultural commitment, but its edges and even its center may have been prime dispersal corridors for other cultural groups.

Culture itself may have been the more formidable barrier to human dispersal. In earlier phases of human evolution, it is possible to imagine that the store of cultural knowledge within any given group would have been fairly low. A population may have expanded to exploit a new habitat without abandoning much of an investment in the old habitat, and the ability of a group to expand or displace other people within a habitat may have relied only in minor ways upon their inherited cultural knowledge. By contrast, the MSA shows signs of greater differences between groups in material culture, suggesting a deeper store of cultural knowledge. Human groups entering new environments without existing human populations would have been able to expand rapidly, but groups entering a previously-occupied habitat niche would face a cultural deficit that would be hard to overcome.

If the dispersal of human populations during the MSA appears to have followed habitat gradients, it may be ultimately for cultural reasons. That scenario is not one in which a mobile grassland population would necessarily have connected other populations that had previously been more isolated. It is a scenario in which an unstable balance of culture areas may have been fluctuating as climate oscillations caused some ecologies to expand and others to contract continent-wide. And again, the sobering reality is the proportion of Africa that does not contribute to our current knowledge of this MSA cultural variability.

Reference

Faith JT et al. (2015) Paleoenvironmental context of the Middle Stone Age record from Karungu, Lake Victoria Basin, Kenya, and its implications for human and faunal dispersals in East Africa. Journal of Human Evolution 83:28-45. doi:10.1016/j.jhevol.2015.03.004

High recent admixture reported for Oase 1

Some readers have asked me what I think of the reporting from the recent Biology of Genomes conference, that Qiaomei Fu and colleagues from Svante Pääbo’s group have demonstrated a very recent Neandertal ancestry for the famous mandible from Peștera cu Oase, Romania. This is the earliest-known “modern” human in Europe, around 40,000 years old. For example, this report from Ewen Callaway: “Early European may have had Neanderthal great-great-grandparent”.

They estimate that 5–11% of the bone's genome is Neanderthal, including large chunks of several chromosomes. (The genetic analysis also shows that the individual was a man). By analysing how lengths of DNA inherited from any one ancestor shorten with each generation, the team estimated that the man had a Neanderthal ancestor in the previous 4–6 generations. (The researchers declined to comment on the work because it has not yet been published in a journal).

I have two thoughts:

  1. This is no surprise.
  2. I’m very pleased that the authors are talking about this work at meetings and that journalists are reporting on the work. I hope that the broader awareness of this work as it is happening will cause other people to find things they might not have noticed before. I also hope that it will not prejudice the publication of this work in a high profile journal, should the authors choose to pursue that route.

OK, I have more than two thoughts, but unfortunately, until I see the details I won’t be able to comment intelligently on most of the interesting questions. I do wonder: Why does anyone think they can tell a Neandertal from a “modern human” in this time period from a tooth?

Of course, all the facts are already on Wikipedia…

No Australopithecus boisei from the Afar

I was reading Scott Simpson and colleagues’ article from March 2014, “The female Homo pelvis from Gona: Response to Ruff (2010)”, in which they go through reasons why the BSN49/P27 fossil pelvis belongs to Homo and not, as Ruff has suggested, some version of Australopithecus or Paranthropus.

I blogged about the anatomy of the Gona pelvis (BSN 49/P27) when it was first published in 2008: “Mrs. Elvis, the Homo erectus pelvis”, and raised all the issues that have since become features of the scientific literature. It is a very interesting problem, because BSN49/P27 is only a pelvis; no other skeletal remains have been found from the same individual. Diagnosing pelvic anatomy as belonging to Homo is an interesting problem right now, because of the lack of evidence about pelvic anatomy in late australopiths such as Australopithecus boisei and the presence of Homo-like features in the pelvis of Australopithecus sediba.

I wanted to flag an interesting observation to which I haven’t given much thought before: Au. boisei has not been found at any of the Afar sites. This comes in Simpson and colleagues’ argument that the Gona pelvis BSN49/P27 must be Homo because only Homo has been found in the area during the same time interval.

Finally, Ruff proposed that the Gona pelvis could possibly have been a representative of a species outside of the genus Homo, such as Au. (P.) boisei. Unfortunately, no fossils were allocated to this species in his analysis. No pelvis of Au. (P.) boisei is known and no Australopithecus have been discovered from the Afar region that are younger than 2.5 Ma. Fossils representing the ‘robust’ group were all from Swartkrans and assignable to Au. (P.) robustus. While assigning the Gona pelvis to Au. (P.) boisei might seem like a possibility, the absence of any known comparative material makes this assignment untestable as it is not based on comparative data.

Later in the paper, they reiterate this point:

Despite significant effort surveying for fossils, no specimens attributable to Au. (P.) boisei are known from the Afar region. The Konso, Ethiopia ( Suwa et al., 1997) specimens are the northernmost representatives currently known. Currently, Au. (P.) boisei is not known from any deposits younger than 1.4 Ma ( Suwa et al., 1997). Thus, the 0.9–1.4 Ma Gona pelvis, if it was assignable to Au. (P.) boisei, would be the unique representative from the Afar region and the last appearance datum for this species.

This is perhaps less surprising than it sounds at first, because there are no other Homo specimens reported from Afar during the time span between the date reported for the A.L. 666-1 specimen (2.33 million years) (Kimbel et al. 1997) and the much later Daka specimens (Asfaw et al. 2002) around a million years old. Based on the stratigraphic information published by Simpson et al. (2008), the Gona pelvis lies either within this gap or at the tail end of it.

Amid such a near-total lack of fossil evidence, I wouldn’t readily dismiss the idea that some late australopith may have been present in the Afar area during the Early Pleistocene.

But what would it mean if Au. boisei and other late australopiths really never lived in the Afar area? An absence from Afar would contrast strongly with the Turkana Basin, where Au. boisei is the most common fossil hominin within the sediments leading up to 1.4 million years ago. The Turkana Basin includes a good fraction of southern Ethiopia, where what may be the earliest occurrence of Au. boisei is in the Shungura Formation. The latest occurrence of Au. boisei is also in southern Ethiopia, near Konso. Some recent species do have biogeographic distributions that suggest a split between northeastern and southern Ethiopia; whether such a split was present or relevant for Au. boisei may be worth investigation.

It is a bit odd that no robust australpiths are yet known from North Africa or West Asia. Theropithecus—the genus including living geladas—existed as far as Morocco and India during the Pleistocene. The usual reconstruction of australopiths would suggest they should have been able to disperse effectively through savanna and along rivers and coastlines. Maybe Au. boisei will yet be found outside of its known Rift Valley range.

References

Asfaw, B., Gilbert, W. H., Beyene, Y., Hart, W. K., Renne, P. R., WoldeGabriel, G., ... & White, T. D. (2002). Remains of Homo erectus from Bouri, Middle Awash, Ethiopia. Nature, 416(6878), 317-320. doi:10.1038/416317a

Kimbel, W. H., Johanson, D. C., & Rak, Y. (1997). Systematic assessment of a maxilla of Homo from Hadar, Ethiopia. American Journal of Physical Anthropology, 103(2), 235-262. doi:10.1002/(SICI)1096-8644(199706)103:2<235::AID-AJPA8>3.0.CO;2-S

Ruff, C. (2010). Body size and body shape in early hominins–implications of the Gona Pelvis. Journal of Human Evolution, 58(2), 166-178. doi:10.1016/j.jhevol.2009.10.003

Simpson, S. W., Quade, J., Levin, N. E., Butler, R., Dupont-Nivet, G., Everett, M., & Semaw, S. (2008). A female Homo erectus pelvis from Gona, Ethiopia. Science, 322(5904), 1089-1092. doi:10.1126/science.1163592

Simpson, S. W., Quade, J., Levin, N. E., & Semaw, S. (2014). The female Homo pelvis from Gona: response to Ruff (2010). Journal of human evolution, 68, 32-35. doi:10.1016/j.jhevol.2013.12.004


Chanda Prescod-Weinstein has written an evocative essay about her experience becoming a physicist, and the daily frustrations and challenges of being different in background from those ordinarily welcomed into the field: “Let Physics Be the Dream It Used To Be”

I’m not going to catalog every shitty thing that happened to me in grad school or as a postdoc even though I haven’t actually mentioned the worst stuff, but the point is that I didn’t and still don’t fit into the dominant astro/physics culture, and this has really sucked a lot of the fun out of physics for me. White astro/physicists need to understand and take to heart that this is in fact a real issue that doesn’t magically go away with admissions and diversity initiatives that fail to address underlying cultural, structural issues.

She reminds us that science as a career choice has many unappealing qualities, particularly for those who lie outside a particular social background.


Many people know the story that Carl Sagan was rejected for membership in the National Academy of Sciences of the United States. The story has given rise to the idea of the “Sagan Effect”, whereby scientists who are active in popularizing and explaining science to the public are perceived by other scientists as being somehow less serious about their research.

Someone asked me about this today and I ran across a quote from the journalist Joel Achenbach, who had profiled Sagan in 1996, in an article reprinted in the book, Conversations with Carl Sagan (Carl Sagan and Tom Head, editors, 2006). This excerpt is from page 158:

In 1992, Sagan's name was one of sixty nominated for membership in the National Academy of Sciences. The other fifty nine made it without a hitch. But someone objected to Sagan.
Sagan's case was argued by Stanley Miller, a chemist who did pioneering work on the origin of life. He believes Sagan's scientific work, such as his research on the atmosphere of Venus, is often overlooked. The anti-Sagan faction countered that if the fluffy stuff of Sagan's career were swept away, there wouldn't be enough hard science underneath.
One member who was present says, "If he had not done television, he probably would be in the academy."

Theodosius Dobzhansky, “Man and Natural Selection” (American Scientist 49:285, 1961):

By changing what man knows about the world, he changes the world he knows; and by changing the world in which he lives, he changes himself. Herein lies a danger and a hope; a danger because random changes of the biological nature are likely to produce deterioration rather than improvement; a hope because changes resulting from knowledge can also be directed by knowledge.

Ars Technica has a long article in honor of the anniversary of the Apollo 13 by writer Lee Hutchinson, giving background to the famous accident that the movie (and books that I’ve read about the space program) omitted: “45 years after Apollo 13: Ars looks at what went wrong and why. I’ve never read such a clear account of why the oxygen tank exploded.

And the real moral of the story:

For Apollo 13, keeping calm and working the problems as they appeared allowed three astronauts to escape unharmed from a complex failure. The NASA mindset of simulate, simulate, simulate meant that when things did go wrong, even something of the magnitude of the Apollo 13 explosion, there was always some kind of contingency plan worked out in advance. Controllers had a good gut-level feel for the limits of the spacecraft’s systems when trying to work through emergency problems.

Esther Ingliss-Arkell has an interesting short description of “What Happens When You Get The Wrong Blood Type?” on io9.

The first sign of a transfusion gone wrong is "a feeling of impending doom." This is a legitimate medical symptom, and doctors who regularly work with blood transfusions are told to look for it. Other sign of a mismatched blood type is the usual immune system warning flags — flu-like fever, ache, and chill, as well as a burning sensation at the injection site.

I teach the ABO system as part of my usual human genetics lectures, and I’ve never read a great description of the range of transfusion reactions—I was really only aware of the most catastrophic type. So this can be an interesting piece for those teaching ABO as well as those who’ve just always wondered.