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I'm currently supervising a graduate student who's writing a review of the literature on tool use in wild chimpanzees. This has become a most enjoyable interaction: it's a topic I've been interested in for quite a while now, so the supervision role is an excuse to extend my own knowledge, and it's great helping the student to enhance their own skills in relation to academic research and writing. 

Anyway, a couple of days ago I came across a new paper (Boesch et al., 2016) on an intriguing aspect of chimpanzee behaviour, and my student and I had a stimulating discussion about it at our regular weekly meeting this morning. (There's a general summary of the findings and the project which generated them here.) I'd previously heard of (& shared with her) what appeared to be an isolated incident of 'fishing' by an orangoutan, but this new paper documents wild common chimpanzees, Pan troglodytes, using a new technique to obtain freshwater algae. (Of interest in the orangoutan example were the claims that the image of the animal in action were faked, claims discussed here and dismissed as false.)

It seems that it's unusual for primates to eat aquatic plants, although they may eat fish and invertebrates when available. Both bonobos (Pan paniscus) and gorillas eat plants growing in swampy areas. Common chimpanzees do the same, but have also been reported eating algae - something that's really unusual in animals apart from marine species. And it's highly unusual in chimps too: 

despite decades of chimpanzee research, there are only a few observations of algae harvesting, suggesting that this behavior is indeed rare

and in most of these observations the chimps used their hands, rather than tools, to scoop algae from the water. It's possible, of course, that the local ecology of other well-studied chimpanzee groups just don't favour consumption of aquatic algae. But this behaviour could also be due to cultural evolution in a few small social groups.

So, Boesch and his team set up a research station at Bakoun, in Guinea (not far south of the equator), as part of a continent-wide attempt to 

contribute to a fuller understanding of the extent of chimpanzee behavioral variation and flexibility

in order to help get a handle on the actual level of behavioural diversity in wild chimps, and to answer questions around the relative effects of ecological diversity and cultural evolution on differences in behaviour shown by different groups of animals.

The chimps in the study area at Bakoun hadn't been studied before, and to minimise the potential impacts of interaction with humans, all observations were made using 'remote video camera traps', triggered to begin recording on detecting movement. These cameras were set up at sites where there was other evidence of chimp activity, such as remains of tools. Obviously they captured much more than chimpanzee activity, but of the 1,473 video clips that showed chimps, 486 (from 11 different sites), showed the animals 'fishing' for algae (Spirogyra sp.). Most of these events happened during the dry season, when water levels were lower, peaking in the 'hot dry' season when chimps returned repeatedly to the same sites over several days. 


The chimpanzees were observed to fish for algae at sites where the algae occurred in large accumulations at the bottom of the river bed.We rarely observed free floating, surface algae being targeted... [and we] observed all age and sex classes perform and succeed in fishing for algae from deep ponds or river shores.

Interestingly, the researchers found that every single animal used a tool to collect algae, even those only 2 or 3 years old - and they tended to use the same hand each time they fished. They fished by holding one end of a long stick, reaching it down to the bottom of the water, and then twirling the stick so that strings of algae were wound onto it. They then withdrew the stick and pulled the algae off with their lips. And, when algae fishing, the chimps usually avoided getting wet as much as possible. 

To see how successful this was as a food-gathering strategy, two of the research team used a discarded chimp tool - they managed to collect 400g of Spirogyra in just 10 minutes. Since individual chimps were seen fishing for an hour at a time, algae fishing could make quite a contribution to their seasonal diet:

chimpanzees may be fulfilling substantial dietary requirements [for protein, carbohydrates, and lipids, plus antioxidants and minerals] by ingesting large amounts of Spirogyra algae during the dry season

And just what were these tools? Mostly woody branches, modified by stripping off smaller branches and fraying one of both ends; some of these branches were up to 4m long, allowing access to algae that was otherwise unreachable in deeper parts of the river. In around 20% of events chimps arrived at their fishing sites already prepared ie bringing tools with them.

As I commented to my student, research like that described by Boesch and his colleagues goes well beyond simply documenting the activities of our close cousins. This is because, while it's likely our own hominin ancestors used a variety of plant-based tools, these aren't the sort of thing that's likely to be found by palaeontologists, and so 

research on primates can illuminate the potential repertoire of tool use behaviors that may reasonably be assumed to have been present in our last common ancestor (Boesch et al. 2016).

For example:

we suggest that in Bakoun, tool use permits a more efficient access to a rarely available but highly preferred resource, such as algae, that permits chimpanzees to flourish in an environment otherwise more limited in food and water. It is therefore probable that our last common ancestor would have similarly made and used tools to also engage in rudimentary fishing, to collect and consume rich aquatic fauna, and perhaps flora too (ibid.).

And

This [research] demonstrates the flexibility in [chimpanzee] technical skills and how this helps them to obtain access to valuable resources in a drier habitat and new context. Such technological skills have been suggested to be present in our human ancestors when they invaded drier, savanna habitat during the course of human evolution (ibid.).

C.Boesch, A.K.Kalan, A.Agbor, M.Arandjelovic, P.Dieguez, V.Lapeyre, and H.S.Kuhl (2016) Chimpanzees routinely fish for algae with tools during the dry season in Bakoun, Guinea. American Journal of Primatology 78(12), published on-line 3 November 2016. DOI: 10.1002/ajp.22613

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I've just come across a most excellent article by the Genetic Literacy Project. In it, Nicholas Staropoli notes that a proportion of the human genome actually has viral origins.

This might sound a bit strange - after all, we tend to think of viruses as our enemies (smallpox, measles, and the human papilloma virus come to mind). But, as Staropoli notes, there are a lot of what are called 'endogenous retroviruses' (ERVs) - or their remains - tucked away in our genome. (An ERV has the ability to write its own genes into the host's DNA.) And he links to a study that draws this conclusion: 

We conservatively estimate that viruses have driven close to 30% of all adaptive amino acid changes in the part of the human proteome conserved within mammals. Our results suggest that viruses are one of the most dominant drivers of evolutionary change across mammalian and human proteomes.

Carl Zimmer writes about one such example in his blog The Loom: it seems that a gene that's crucial in the development of the placenta (that intimate connection between a foetus and its mother) is viral in origin. In fact, one gene encoding the protein syncytin is found in primates - but carnivores have a quite different form of the gene, while rabbits have a different form again, and mice yet another!

This is a very complex evolutionary story indeed. And so you could do much worse than read the two articles, by Staropolis and Zimmer, in their entirety. 

 

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Demodex mites are tiny little creatures that live in mammals' hair follicles. I first heard about them years ago, when I watched a documentary with my science class back at PN Girls' High. It was about animals that are parasitic on humans, and after the segment on eyelash mites, I don't know about the girls but I felt itchy for days!

For eyelash mites live where the name suggests, in the follicles of our eyelashes. (There are 2 species: Demodex folliculorum and D. brevis.) The common name gives an idea of just how small they are: adult length is 0.3 to 0.4 mm. They spend a lot of time inside the eyelash follicles, snacking on the sebum and dead cells (or maybe the bacteria) that accumulate there. But at night... at night, they come out and wander across our faces as we sleep, achieving a speed of 10cm/hr or more. Which doesn't sound much, but when you remember how small they are, that's quite an achievement. Presumably that's also when they mate, which they do where an eyelash follicle opens to the skin's surface. 

I was surprised to discover that these mites lack an anus. This sounds somewhat problematic, but the eyelash mites have survived, with their human hosts, for at least tens of thousands of years, so they obviously cope somehow. And when they die, their little bodies degrade and release their contents. On your face. Or in the follicles where they spent most of their lives.

Though demodex mites are tiny, there are an awful lot of them. There may be only one or two per hair follicle (they don't restrict themselves to the eyelashes), but an individual human has around 5,000,000 hairs on their body (Thoemmes et al., 2014), so that's an awful lot of available places for a mite to set up home in.

Thoemmes & her co-workers were interested in the genetic diversity of these mites. They predicted there'd be geographically-distinct lineages, because the tiny animals are very closely associated with their hosts and don't seem to be particularly mobile between hosts. However,

if Demodex lack strong geographic structure, it suggests the movement of mites among humans must occur very frequently (perhaps even with social greeting rituals) and across large geographic distances.

To test this hypothesis, the team examined adults (from a single North American population) visually, but also tested skin scrapings for the presence of mite DNA. The results showed that despite being able to see mites on only 23% of their sample population, 16S rDNA sequencing indicated that 100% of those sampled actually had mites present. The latter matched other research showing that 100% of dead bodies tested positive for the presence of Demodex.

Figure 2 from Thoemmes et al. (2014): Maximum likelihood (ML) phylogeny of mites based on 18S rDNA sequences.

While the results of their phylogenetic analysis of the mite DNA are based on samples from only 29 people, they're interesting nonetheless. It appears from that analysis that the 2 species, D.folliculorum & D.brevis, probably colonised humans at different times. Because D.brevis' DNA indicates that their nearest living relatives are mites living on dogs, then the researchers suggest that we acquired this species from our doggy friends, perhaps as recently as 11,000 years ago but possibly as many as 40,000 years ago. There does appear to be some regional variation (based on a comparison of the US data with earlier sequencing results from Chinese populations), but there's also quite a bit of variation within populations, due perhaps to individual humans picking up different mites on different occasions as individual humans came into close physical contact.

And after reading all this & watching a few videos, I feel itchy again!

Thoemmes MS, Fergus DJ, Urban J, Trautwein M, Dunn RR (2014) Ubiquity and Diversity of Human-Associated Demodex Mites. PLoS ONE 9(8): e106265. doi:10.1371/journal.pone.0106265

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Well, probably not1, in the sense that most would place on the term 'tummy bug' (where a close proximity to the toilet is a Good Thing), but it turns out that he did have some rather interesting intestinal bacteria.

Ötzi is perhaps better known as the 'Iceman', who died around 5,300 years ago in the Otztai Alps of the Italian Tyrol. (He's the subject of a fascinating web page & I have to say, I'd love to visit the museum, maybe when we next visit family in Europe.) His body, clothing, and equipment are exceptionally well-preserved & are yielding a great deal of information on life in Neolithic Europe - including, as described in the latest issue of Science, the nature of his microbiome. (You'll find the full paper here, but there's also an open-access summary here. I do have a gripe about the use of the term 'tummy bug' in the latter, though!)

In their just-published paper, Maixner's research team reports on their finding of a strain of Helicobacter pylori in Ötzi's stomach contents (he'd apparently eaten a full meal not long before he died). I've written about H.pylori before: while it's been found to be associated with development of gastritis, stomach ulcers, & sometimes cancer in a small proportion of those carrying it2, there's also evidence that it has a protective effect against other disorders, including acid reflux and oesophageal cancer. And it's been with us for a long time:

Predominant intrafamilial transmission of H. pylori and the long-term association with humans has resulted in a phylogeographic distribution pattern of H. pylori that is shared with its host. This observation suggests that the pathogen not only accompanied modern humans out of Africa, but that it has also been associated with its host for at least 100,000 years. Thus, the bacterium has been used as a marker for tracing complex demographic events in human prehistory.

Most modern Europeans carry one particular strain of this bacterium, which is believed to have originated via recombination of two earlier strains. However, the origins of these strains have been uncertain, & the researchers hoped that Ötzi's gut microbes might throw some light on this. The Iceman himself was born and lived in Southern Europe, and DNA comparisons link him to early European farmers. However, the strain of H.pylori found in his gut is most closely related to a haplotype now found in central and southern Asia, and not to those of Europe and Africa.

The detection of an hpAsia2 strain in the Iceman’s stomach is rather surprising because despite intensive sampling, only three hpAsia2 strains have ever been detected in modern Europeans. Stomachs of modern Europeans are predominantly colonized by recombinant hpEurope strains.

Maixner suggests that the Iceman's ancestors must have brought this Asian strain of H.pylori with them when they migrated to Europe. Well after Ötzi died, later immigrants from Africa brought their own strain of the bacterium, and subsequent recombination produced the modern European strain of this microbe. This is evidence for rapid evolution of H.pylori in Europe as waves of human migrants moved into and across the continent.

The researchers also noted that Ötzi's version of the bacterium represents a strain that's associated with stomach inflammation in modern humans - and that protein biomarkers expressed in his gut indicate that he had an inflammatory response to the infection. This may or may not have manifested in actual disease - his stomach lining was not sufficiently well-preserved to let them draw any conclusions on this.

 

1  Which is a real pity, as I was so going to steal my friend Grant's suggested phrase, "the Tyrolean trots", for my title :( 

 It's "found in approximately half the world’s human population, but fewer than 10% of carriers develop disease that manifests as stomach ulcers or gastric carcinoma" (Maixner, Krause-Kyora, Turaev, Hoopmann et al., 2016)

F.Maixner, B.Krause-Kyora, D.Turaev, A.Herbig, M.R.Hoopmann, J.L.Hallows, U.Kusebauch, E.Vigi, P.Malfertheiner, F.Megraud, N.O'Sullivan, G.Cipollini, V.Coia, M.Samadelli, L.Engstrand, B.Linz, R.L.Moritz, R.Grimm, J.Krause, A.Nebel, Y.Moodley, T.Rattei, & A.Zink (2016) The 5300-year-old Helicobacter pylori genome of the Iceman. Science 351 (6269):162-165 . DOI: 10.1126/science.aad2545

 
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Why is it that practically every time there's a new discovery relating to the evolution of our own species, there is a headline saying that this finding 'could rewrite human history'?

Because, bingo! At least one newspaper report1, of a paper published last week in Nature, carried the header: "Homo erectus engraving could re-write human history, and might show art began 300,000 years earlier than we knew." 

Now, the story's really interesting & surely didn't need the overblown headline, even if one of the research team was reported as using the phrase. Certainly the work of a large team of researchers (Joordens et al, 2014) has pushed back the dates for human use of symbols, to around 0.5 million years ago (on the basis of 40Ar/39Ar and luminescence dating), which is far older than the carvings and paintings of Cro-Magnons, and perhaps Neandertals - but doesn't necessitate a total rewrite of our history. And if their attribution of the finds to erectus is correct, then it extends our understanding of cognition in this species. (In fact, headlines like that fall right into the hands of creationists.)

This is a nice piece of detective work, & it also shows how serendipitous some discoveries can be: one of the team, Stephen Munro, noticed the marked mussel shell in photos he'd previously taken of specimens in a museum collection in Leiden, and that sparked a thorough investigation of the provenance and age of the shells. It turns out that the shell assemblage was originally collected at Trinil in Indonesia - the same location, and in fact the same strata (the 'main bone layer') as that of the 'type' specimen for H.erectus, collected in 1891 by Eugene Dubois. This led the team to the conclusion that this marked shell, and what looks like intentional damage to other shells, were the work of Homo erectus.

So what can we tell from these results? Well, it looks as if erectus enjoyed a good feed of seafood from time to time. The evidence for this lies in shells with holes in them - holes that lie over the position of the adductor muscle that holds the shell closed. Around 1/3 of the shells from this particular site had these holes, & overall the shell assembly contained "only large adult-sized specimens (about 80-120mm in length), while under normal conditions mussel populations contain all size classes" (Joordens et al, 2014): this strongly suggests that the molluscs were deliberately collected.

As for the holes themselves - the research team ruled out the possibility of damage by non-human predators, but noted that comparable holes were made in gastropod shells by pre-Hispanic modern humans living in the Caribbean. They went on to experiment on modern mussels and found that someone could use a tool such as a shark's tooth to drill a hole in the animal's shell over the adductor muscle; piercing the adductor caused the bivalve's shell to open. This speaks both to erectus' ability to conceive of and use rather smaller tools than we usually associate with them, and to their knowledge of shellfish anatomy. (You'd certainly find molluscs opened this way much easier to eat than if you had to bash them with a rock!) Another shell appears to have been retouched using a flaker, presumably for use as a scraper or other tool. 

The team then looked at the geometric lines found on the outer surface of one shell & determined that they were highly unlikely to be due to the shell knocking around with other shells & stones, but were probably produced using a shark's tooth or something similar. The lines were most likely laid down while the shell was fresh & so covered with the coloured periostracum common to mussels, "which would have produced a striking pattern of white lines on a dark 'canvas' " (ibid.) The lines are quite deep, would have required a fair bit of force and also good manual control to make, and Joordens & her colleagues concluded that "a single individual made the whole pattern in a single session with the same tool" (ibid.).

So, we've got evidence of what may be the earliest known use of a shell as a tool; evidence of Homo erectus including seafood in their diet; and evidence of someone consciously & deliberately scoring lines in a fresh mussel shell. But was it 'art'? And does it really necessitate the rewriting of our entire evolutionary history?

 

1 I'm not sure why the Independent reporter correctly identified the engraved lines as being on a shell & then went on to talk about them being on 'a rock'. Poor subbing?

 

J.C.A.Joordens, F.d'Errico, R.P.Wesselingh, S.Munro, J.de Vos, J.Wallinga, C.Ankjaergaard, T.Reimann, J.R.Wijbrans, K.F.Kuiper, H.J.Mucher, H.Coqueugniot, V.Prie, I.Joosten, B.van Os, A.S.Schulp, M.Panuel, V.van der Haas, W.Lustenhouwer, J.J.G.Reijmer & W.Roebroeks (2014) Homo erectus at Trinil on Java used shells for tool production and engraving. Nature  doi: 10.1038/nature13962, published on-line 3 December 2014

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The 'paleo' diet story on Campbell Live tonight spurred me to finish my review of one of the most entertaining popular books on genetics that I have read for some time. Entertaining, and informative, in equal measure. I wonder what author Marlene Zuk would have made of the TV story.

book cover

Marlene Zuk (2013) Paleofantasy: what evolution really tells us about sex,diet, and how we live.  Norton (New York)

ISBN 978-0-393-34792-0 (paperback)

For in that story we heard gems like this: "It's a commitment to eating food that is unadulterated, eating food in its most natural state." Paleo proponents (says the TV story) believe our most natural diet is that of our Palaeolithic cavemen ancestors. Somehow I doubt our 'cavemen' ancestors were eating avocados, beetroot, bacon or kale. (There's also an air of chemophobia, with one proponent of paleo eating stating that their diet contains "[n]othing nasty and nothing you can't pronounce" - which reminded me of the series of posters by Australian teacher James Kennedy, showing the list of chemical compounds found in natural food items: blueberries, anyone?).

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I saw this story in the newspaper yesterday, & again today on one of the science feeds

Researchers in the US have studied the skulls of ancient human ancestors and concluded that fist-fighting may have played a role in shaping the male face.

You can read the paper itself here (Carrier & Morgan, 2014). I'm sorry, but to me it reads like a just-so story. Just because modern humans take a swing at each other from time to time, doesn't mean that this was the case for earlier hominins. The authors of the paper argue that the facial features of robust australopithecines are the result of natural selection acting through bare-fist fighting. However, they don't offer any actual evidence that this might have happened: nothing on whether paranthropine skulls show the sort of facial damage that you might expect if fighting in this way was sufficiently widespread to act as a selective force. And similarly, no real discussion of whether Paranthropus could form a fist capable of doing such damage. (The paper on Australopithecus sediba to which they refer actually describes sediba's hand as a mosaic of features.) In other words, they're making a sweeping assumption - that paranthropines routinely beat the heck out of each other - to support the a priori assumption that our own facial evolution was shaped by this.

There's also the question of whether modern human faces show much evidence of having evolved in this way; they actually seem quite prone to damage. Noses & cheekbones are rather susceptible to damage, and the bones of the cranium - thinner than those of Paranthropus - are dangerously easy to break. At the same time, according to the authors' speculative view, our hands are particularly well adapted to deliver blunt-force trauma.

This quote from the paper (emphasis mine) says it for me; we really are dealing with conjecture & imagination: 

Starting with the hand of an arboreal great ape ancestor, it is possible to imagine a number of evolutionary transformations that would have resulted in a club-like structure adapted for fighting.

Rudyard Kipling might have appreciated it - a point also made by Brian Switek in his excellent commentary over at National Geographic.

Carrier, D. & Morgan, M. (2014) Protective buttressing of the hominin face. Biological Reviews doi: 10/1111/brv.12112

 

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In posting an item about the 'pig-ape hybridisation' suggestion for human origins, the Daily Mail is a) coming rather late to the story (a slow day in the newsroom, perhaps?) and b) showing more regard for sensationalism than for good investigative journalism.

The story's one I've posted about before (& I've reposted my original piece below). Seeing it again really makes me think that the originator of this particular idea is trying to have it both ways. If our morphology is as similar as he claims to that of pigs, and different from chimps, then the differences should show up in our genes. Yet they don't; genetically we are much closer to chimps than to swine. He claims that this can be explained by repeated back-crossing with early humans - which is effectively no more than special pleading (& conveniently ignores the issue of significant differences in chromosome number between the two taxa). 

 

The internet is a wondrous place: a source of information, of amusement, and - alarmingly often - of material that elicits a combination of 'say what?' and <head-desk>. And a hat-tip to PZ Myers for this particular example...

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Last year's Schol Bio paper contained (as is usual) some interesting and challenging questions. One of them was about earwax. More specifically, the earwax phenotypes 'dry' and 'wet', and what their distribution can tell us about patterns of human evolution. (Note to those sitting these examinations: most questions have a reasonable amount of resource material provided and this one was no exception. Remember to use this information in your answers! Ignoring it, or - just as bad - copying bits rather than incorporating the material properly - is not a sign of a good response.)

I was particularly interested in this question because we used to look at the distribution of various phenotypes, wet & dry earwax among them. The examiner provided information about the nature of the genetic information underpinning the two phenotypes, along with data about the global distribution of people with wet & dry wax in their ear canals, including a very helpful map. The following graphic is not that map, but is very similar - showing allele frequencies rather than the phenotype distributions used in the exam - & accompanies an excellent blog post on the Discover magazine site. The 'A' and 'G' represent the 2 alleles involved in determining the relative dampness of your earwax: 

Earwax is wet unless an individual has Adenine (A) at a particular site instead of Guanine (G), in which case the wax becomes the dry form. People who inherit the version of the gene that has A from both parents have dry earwax. People who inherit two of the G versions, or one G and one A, have wet earwax.

The actual question asked candidates to

use biological knowledge, together with information from the resource material, to discuss:

  • the origins and inheritance patterns of dry earwax
  • the evolutionary factors that may have resulted in the present-day distribution of both types of earwax.

And as always, a successful candidate would address all parts of a question. Nor would they assume that the examiner 'knows' what they know - you do need to spell out your understanding. 

So, for the first bullet point: we're dealing with a substitution mutation, where a change in a single base (from G to A) has led to a single amino acid change in the final protein. That secretory protein's function is altered so that the wax that's produced is now 'dry'. The mutation must have occurred in a gamete-producing cell, or at the least during meiosis, & subsequently entered the human population's gene pool. We know it's a recessive mutation as someone must be homozygous for the allele to express wet wax, while heterozygotes have dry earwax. And you could also add that it's not a sex-linked mutation, because (as the resource material notes) the gene involved in wax secretion is found on chromosome 16.

The second part of the question requires you to relate the information on the distribution of 'dry' & 'wet' wax phenotypes to your knowledge of patterns of human dispersal (in this case, the 'out-of-Africa' model). The fact that there's no 'A' allele in African populations suggests that this mutation must have arisen after our species started to spread out of Africa. Furthermore, it could well have appeared once a small founder population had arrived in China, with subsequent genetic drift removing the dominant (G) allele from that founder group - this would explain the very high frequency of the A allele (up to 100%) in that region. You could also argue the possibility of positive selection pressure on this version of the secretory protein (an idea critiqued by the author of the Discover blog post).

However, the A allele is also found at fairly high frequencies in other Asian countries - the most likely explanation here is that subsequent migration and interbreeding has introduced it to those populations (with 54% of Indians and 69% of Japanese now expressing the 'dry' phenotype). Until fairly recently there was only minimal migration from China into Russia & Europe, which accounts for the very low frequency of the recessive allele in those populations.

What about the Americas? Our current understanding is that humans migrated into North America from Asia via a land bridge across the Bering Strait, during a glacial period. (There's an interesting discussion around this here, including some work done using a molecular clock based on mutations in the common human pathogen Helicobacter pylori to estimate migration paths & times.) In dealing with this part of the question, I can think of a couple of options: that the lower frequency of the A allele in native American peoples reflects a founder event where the allele was at lower frequency to begin with, & subsequent genetic drift; or that the A allele frequency originally reflected that in Asian populations, but was diluted by a significant drop in population size following European settlement & some later interbreeding with the settlers. Simiilarly, the low A frequency in non-native Americans simply reflects their relatively recent arrival from Europe.

Who'd have thought that the story of earwax could be so fascinating?

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Among other things, I like to knit. My mother got me started, years ago, & I worked up to quite complex Fair Isle patterns on jerseys & shawls. But the kids weren't all that keen on wearing woolly stuff once all the new 'manmades' came on the market, & a well-made jersey lasts a Long Time (30 years, in the case of one of mine), so the knitting took a bit of a back seat & I've only recently got back into it.

Anyway, I was talking about my latest project ** with some friends and Renee said, "I greatly admire people who can take two sticks and some fluffy string and turn it into clothes." At which point I thought: I bet that from a cultural evolution perspective, you could characterise the invention of string as a rather significant innovation. After all, sans string (or some form of fibre - & this would include animal sinew as well as plant fibre) there'd be no woven fabrics; no sewn garments; no nets or string bags to catch things or carry the catch home; no bows (& thus no arrows); no adzes bound to hafts or knives to handles; no sticks tied together into tripods or shelter frames... 

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