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Posts Tagged humanevolution

the amazingness of lyrebird vocalisations Alison Campbell Nov 12

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This is one impressive lyrebird – laser guns and kookaburras! (Not quite at the same time.) I found him on a ScienceAlert page, which has more info and also links to other videos of these vocally talented birds.

how old is a piece of string? Alison Campbell Aug 22

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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… 

By itself, the idea of twisting thread or cordage isn’t all that complex, in technological terms. But in cognitive terms? Well, that’s something quite different, because of the abstract thought required to generate concepts of what that string could be. And in addition, there’s the actual manufacturing complexity involved: 

Process complexity can be illustrated by the example of a bag made out of string consisting of twisted grass. In terms of materials, the bag simply consists of string, which in turn consists of grass, and it can be described as low in complexity. In terms of process, however, the bag might involve tying a series of knots for the main body of the bag, and a series of different knots for the mouth of the bag, with perhaps a drawstring as well, and is likely to require considerable time and skill to manufacture; in this respect, the bag is high in complexity (Rugg, 2011).

The problem is, of course, that fibres don’t tend to survive well over long periods of time: currently the earliest-known remains of actual fibre products date back ‘only’ around 34,000 years‘, which is still amazingly old for relatively easily-degraded materials.  (See also this earlier post of mine.) This is certainly nowhere near as long as the other artefacts with which they may have been associated, although those associated artefacts may still speak to the existence of fibre technologies.  For example, Shea & Sisk (2010) suggest on the basis of what appear to be ancient arrowheads that "complex projectile technology" (bows & arrows, but also spear-throwers & the darts they were used to fling) were developed at least 50,000 years ago (possibly even longer). 

These authors also suggest that the technological advances that fibres enabled may well have had a significant impact on our evolution and dispersal; for example, through improving hunting efficiency. These tools would also have made hunting less perilous, allowing hunters to kill at a distance  - & so, alas, also had an impact on our ability to kill each other. There’s an interesting graphic showing the interplay between genetic, environmental, cognitive & cultural factors and their potential for human expansion here.

So there you go, Renee: my bits of fluffy string (& perhaps even the two sticks I use with them) have a history that goes back at least 50,000 years :) 

G.Rugg (2011) Quantifying technological innovation. PaleoAnthropology 2011:154−165. Doi:10.4207/PA.2011.ART49 (NB written from a mathematical perspective)

J.J.Shea & M.L.Sisk (2010) Complex Projectile Technology and Homo sapiens Dispersal into Western Eurasia PaleoAnthropology 2010: 100−122. doi:10.4207/PA.2010.ART36

 

** This is what started the discussion.

‘a newly discovered species of little people’ Alison Campbell Nov 09

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When the news first came out that Prof Mike Morwood & Thomas Sutikna were going to be giving a public lecture about Homo floresiensis, I was first excited & then seriously annoyed: yay! great topic, but rats! can’t get down to it.

So I was absolutely delighted to see the following in this week’s Royal Society news alerts. I get to hear it after all :) (And many thanks to David Bibby!)

 

8. Virtual event: ‘A newly discovered species of Little People’, 1 December

Note: Thanks to Professor David Bibby, Dean of Science, Victoria University of Wellington, this event will now be live streamed: https://new.livestream.com/i-filmscience/homofloresiensisDec2012

Coinciding with the celebrations centred around the much anticipated World Premiere of Peter Jackson’s Hobbit film, you are invited to attend a free public lecture on Homo floresiensis – a new human species discovered in 2003 on the Indonesian Island of Flores.  This new species is commonly referred to as the “Hobbit” – since it stood just over 1 m tall, had large feet and was capable of undertaking quite complex activities.

Two of the principal archaeologists involved in this remarkable discovery — Professor Mike Morwood (University of Wollongong, Australia) and Thomas Sutikna (Pusat Arkeologi Nasional, Indonesia) — will talk about the Hobbit’s discovery as well as ongoing excavations that seek to better understand this new and unique species of human. 

This event is generously sponsored and supported by Victoria University of Wellington, Te Papa, Wellington City Council, the Embassy of the Republic of Indonesia, and the NZ-Indonesian Friendship Council.

Details: 3 pm Saturday, 1 December, free public presentation & exhibition, Soundings Theatre, Te Papa.

Bookings are essential.  RSVP by emailing  with ‘Little People’ in the subject line or call 04 472 1000.

the origin of modern humans – free webinar Alison Campbell Sep 07

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This comes at an opportune time for those of you teaching the Human Evolution content – and for those looking around for some follow-up reading :-) The Howard Hughes Medical Institute has a whole lot of free biology education resources available on line, and this upcoming webcast looks to be wonderful stuff: Bones, Stones, & Genes: the origin of modern humans. It’s completely free; you just need to register for it. You can bet I’ll be doing my best to be there!

And hat-tip to PZ, who as usual finds out about these things first :-)

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another missing link… Alison Campbell Apr 05

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This morning’s NZ Herald carried a story from the UK Telegraph under the headline “Child’s skeleton missing link to man’s ape-like forebears.’ It could have been worse: the Telegraph‘s headline was ‘Missing link between man & apes found’ (sigh). I read the article & have to confess a certain amount of disappointment – because this seems to be another case of the press release pre-dating the actual scientific paper describing the remains. (A bit like all the hoo-rah surrounding ‘Ida’, really. And one has to wonder why this is so.)

The new fossil appears to be contemporaneous with Homo habilis, & in fact the story suggests that it may provide a link between habilis & the more ‘ape-like’ australopiths (an interesting idea, given that habilis is itself fairly similar to the australopiths in many ways). Regardless of this, it does sound like an interesting specimen, given that it’s described as ‘an almost-complete skeleton’ in the Telegraph story.

But some of the statements seem rather overblown – we’re told that the skeleton ‘will allow scientists to answer key questions… [such as] when they began walking upright on two legs.’  Yet we already know that the trend to bipedalism began much earlier than this (& may even have been a trait found in the most recent common ancestor between chimps and humans), so this is not really a biggie. And while the new fossil may well prove to fill some gaps in our knowledge of our family tree, it is not going to have us ‘rewrite the story of human evolution’! (Several of the experts quoted in the story qualify their statements with ‘may’ & ‘if’ &  ‘could’: they too will be waiting with interest for the actual release of the full scientific description of this find.)

I would love for this new fossil to be a clear window into our past. But I wish, oh how I wish, that press release and scientific paper could have appeared together, instead of the media flurry preceding the information that would let us make sense of it all. Not least because, by the time the actual paper comes out – later this week, according to the Telegraph release - the ‘yet another missing link’ idea will be firmly at the front of people’s minds, with all the polarisation of opinion that this implies. (Read the comments following the news story, to get a feel for what I mean.)

a new hominin from siberia? Alison Campbell Mar 29

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ResearchBlogging.org

The latest edition of Nature carries an item that raises the possibility of another new – & recent – new hominin species, this time from Siberia (Krasuse et al., 2010). A few years ago, when the story about Homo floresiensis first broke, I remember commenting to my classes that it was probably only a matter of time until another recent relative popped up. After all, all the evidence to date shows that our family tree is much bushier than scientists used to think – when I was in high school that tree was presented as essentially linear in nature. But Siberia?

My mother used to say (when asked by importunate students how old she was), ‘I’m as old as my little finger & older than my teeth.’ In the case of this possible new hominin, that would make her very old indeed. The new find consists of a finger bone – the tip of a pinky, in fact – and the mitochondrial DNA (mDNA) extracted from it. (For ‘pinky’ read ‘distal manual phalanx of the fifth digit’…)

The bone was found in Denisova Cave, which is in the Altai mountains of Russia & which has been occupied (on & off) by hominins for around 125,000 years. The finger bone wsa found in a layer of sediment dated at 48-30,000 years ago, & which has also yielded a range of other artefacts. Krause & his team decided to see if they could extract & sequence mtDNA from the bone; they felt this was at least a possibility as the cool conditions in the cave are better for long-term preservation of DNA than the tropics. They expected that – if their extraction was successful – the bone would be from a Neandertal or a modern H.sapiens individual, on the basis of the tool assemblages from the site and the geographic range of both species.

Using 30mg of powdered finger bone (this sounds like something Macbeth’s witches would have liked…), the research t3eam were able to extract & sequence mtCNA. They then made a section extract & compared the two sequences: they turned out to be identical. The team hen checked that their sequences came from a single individual (if one bone yielded evidence of more than individual, then there could be questions about contamination). It did.  The degradation patterns of all the mtDNA fragments were also typical of ancient, not modern DNA: further evidence that the sample was not contaiminated.

The next step was to compare the mtCNA from the Denisova cave individual with sequences from  modern human mtCNA, a sample from an individual who lived in late-Pleaistcene Russia, Neandertal mtCNA, and sequences from a chimp and a bonobo. There must have been a certain amount of excitement in the lab when the results of this came out – becaue the Denisova hominin’s DNA had nearly twice as many idfferences from modoern DNA as that of Neandertals (385 base-pair differences for Denisova/sapiens compared to 202 for the Neandertal/sapiens comparison). 

This suggests that the most recent common mtCNA ancestor for modern humans, Neandertals, & the Denisova individual lived about a million years ago.There’s a certain amount of uncertainty around the dates, but nonetheless this is a long time ago. Krause’s team comment that  ‘the divergence of the Denisova mtDNA lineage on teh order of one million years shows that it was distinct from the initial radiation of H.erectus that first left Africa 1.9 million yeers ago.’  Remember, though, that we really need DNA (ideally both mitochondrial & nuclear) from more complete skeletal remains before it’s possible to ‘place’ the Denisova hominin with any degree of confidence.

Getting back to my original comment – it’s entirely possible that multiple hominin lineages co-existed in this part of the world as recently as 40,000 years ago. If the Denisova individual is confirmed as a new species, then it would have had both Neandertal & anatomically-modern humans as close neighbours in space & time. The apparent temporal overlap of floresiensis and sapiens in Indonesia may not have been an isolated event, and our family tree will then be even bushier than my teachers ever imagined :-) 

Krause, J., Fu, Q., Good, J., Viola, B., Shunkov, M., Derevianko, A., & Pääbo, S. (2010). The complete mitochondrial DNA genome of an unknown hominin from southern Siberia Nature DOI: 10.1038/nature08976

knuckle-walking – not an ancestral trait in humans Alison Campbell Oct 06

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After writing about ‘Ardi’, I remembered that this wasn’t the only paper I’d read recently suggesting that our ancestors were not knucklewalkers and that knuckle-walking must have evolved independently in the gorilla & chimp lineages. (We can say this because, if the last common ancestor of chimps & humans didn’t get around by knuckle-walking, then neither did the earlier last common ancestor of chimps-humans & gorillas.) Also in my ‘to write about’ folder is a paper by Tracy Kivell & Daniel Schmitt (2009), entitled Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor.

As Kivell & Schmitt note, scientists have been debating the origins of bipedalism in humans for many years, focusing on whether we evolved from some knuckle-walking ancestor that must have spent much of its time on the ground, or from an animal that still lived in the trees. I suspect that knuckle-walking has had the upper hand (sorry!) for a while, although the relatively early development of bipedalism must have given some pause for thought - even before the latest flurry of publications on Ardipithecus ramidus, there were suggestions that this species was probably bipedal.

Up until fairly recently, the arguments were based around evidence (or lack of it) for adaptations for knuckle-walking in the various members of the human lineage. The other side of the coin, of course, would be evidence for this behaviour in our closest living relatives, the chimps & gorillas, and in other primates. Kivell & Schmitt decided to evaluate this evidence, collecting data on supposed knuckle-walking characteristics in apes & monkeys & then "[using] these data to test the hypothesis that all knuckle-walking apes share similar anatomical features and that these features can be used to reliably infer locomotor behaviour in our extinct ancestors" (2009). In other words, if the same suite of physical features were found in all African apes, then we could safely assume that they were knuckle-walking adaptations that were also present in the last common ancestor of chimps & hominins. If, however, these features differed between chimps & gorillas, then all bets would be off – it would suggest convergent evolution in these groups & make it much less likely that the earliest hominins also had this trait.

Kivell & Schmitt found that a number of earlier papers had listed features linked to knuckle-walking, largely to do with the bones of the wrist, which limited extension of the wrist. It turned out, though, that many of the studies involved rather small sample sizes & were often restricted to chimpanzees alone; nor did these studies look at how the features changed during development (eg the amount of curvature in chimp finger bones changes as individuals grow & spend more time actively moving around in the trees.)  So Kivell & Schmitt made sure that they examined developmental changes in the wrists of chimps, gorillas, & other primates, in addition to simply comparing the presence & extent of the various features they were interested in.

Rather to their surprise, the authors found that there wa a lot of variation in wrist structures of adult African apes, to a degree that "casts doubt on the assumed functional link between specific aspects of wrist morphology and knuckle-walking behaviour" (Kivell & Schmitt 2009). What’s more, most of the gorillas in their sample didn’t have the key features that scientists had always thought were needed to restrict wrist extension while knuckle-walking. Other supposed knuckle-walking features, while present in adult chimps, were also found in non-knuckle-walking monkeys – & were rare in gorillas. When they looked at the biomechanics of this form of locomotion, they found that chimps knucle-walk with their wrists in a relatively extended position, while gorillas have what they described as a "neutral, columnar hand posture" – the differences appear to be related to environment, with gorillas being more terrestrial.

These differences strongly suggest that knuckle-walking evolved independently in chimps & gorillas. Kivell & Schmitt concluded that "[the] presence of purported knuckle-walking features in the hominin wrist can thus be viewed as evidence of arboreality, not terrestriality, and provide evidence that human bipedalism evolved from a more arboreal ancestor…" The new descriptions of Ardipithecus certainly provide strong support for that conclusion.

T.L.Kivell & D.Schmitt (2009) Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor. Proceedings of the National Academy of Sciences 106 (34):14241-14246 doi 10.1073.pnas.0901280106

the ‘missing link’ disproved? Alison Campbell Oct 03

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A friend of mine’s sent me an item from National Geographic with the headline ‘Oldest "human" skeleton found – disproves "missing link"’. (Thanks, Heather!) The story itself is based on the publication this week of a series of papers describing aspects of Ardipithecus ramidus, & they make extremely interesting reading. But before I start talking about them, please allow me a little vent…

really dislike headlines like this! OK, they attract attention, but… Essentially what it’s saying is that the last common ancestor that humans share with our sister species, chimpanzees, wasn’t particularly chimp-like, so we can kiss the idea of that sort of ‘missing link’ goodbye. But is there any good reason why that last common ancestor might have been like modern chimps? After all, they’ve been progressing down their own evolutionary path over the last 6 million years or so, just like us. The article also notes that ‘Lucy’ aka Australopithecus afarensis is no longer ‘it’. But then, at 3.2 million years old, she was always going to be too young to be even remotely representative of that common ancestor, which DNA analyses suggest lived around 6my ago. Anyway, back to the chase…

Despite all the hype, Ardipithecus ramidus isn’t new to science. The species was first discovered in 1992, and at 4.4my old has long been considered the earliest known confirmed  hominin. (The older Orrorin tugenensis is too fragmentary for scientists to be confident of its relationship to our own lineage, although that’s where its discoverers place it, & it’s the same for Sahelanthropus tchadensis.) Since then, a large number of scientists have been examining not only the fossil remains of this species, but also a range of other materials that have allowed them to take an extremely thorough look at its environment. The result: 11 papers published in the 2 October edition of Science – they’ve been made freely available; you just need to register here to access them. So make no mistake; this is a uniquely detailed presentation of the biology & ecology of an early hominin, a story that’s been nearly 20 years in the making (unlike the rushed presentation of ‘Ida’ to the world!). As the editors of Science say:These 4.4 million year old hominid fossils sit within a critical early part of human evolution, and cast new and sometimes surprising light on the evolution of human limbs and locomotion, the habitats occupied by early hominids, and the nature of our last common ancestor with chimps.

One of those 11 key papers is Ardipithecus ramidus and the palaeobiology of early hominids (White et al. 2009). (It’s accompanied by an ’authors’ summary’ that outlines the physical features of ramidus & places it in an ecological context – this would be good for students to read as an entry point to the full scientific paper.) The authors have used existing & new material – and among the fossils they used is the partial skeleton of one individual, dubbed ‘Ardi’.

Fig. 3 from White et al. (2009): The ARA-VP-6/500 skeleton. This is a composite photograph to show the approximate placement of elements recovered. Some pieces found separately in the excavation are rejoined here. Intermediate and terminal phalanges are only provisionally allocated to position and side.

Isn’t that lovely? And isn’t it wonderful that so much of this individual has survived for such a long period of time. Fossilisation of terrestrial animals is relatively rare, & finding such fossils can be very difficult & entails a certain amount of luck. As White & his colleagues note, "bones of medium & large mammals were usually ravaged by large carnivores, then embedded in [sediments]. Once exposed by erosion, postdepositional destruction of the fossils by decalcification & fracture is typical."  That was certainly true for the remains of this individual, which were extremely fragile – to the extent that it took several years to restore. Other fossils found in the same strata suggested that ramidus lived in wooded habitats, not open grasslands. This gives food for thought as up until now we’ve thought that early human evolution was linked to the expansion of grasslands.

The skeleton represents the remains of a female who would have been around 120cm tall & weighed about 50kg. Its cranial capacity was small, around 350cc (much the same as Sahelanthropus) & the face was prognathous, although less so than modern great apes. Teeth can tell us a lot about diet, & those of Ar. ramidus suggest that it was omnivorous & didn’t eat particularly hard foods. In addition to wear patterns on the teeth, the scientists used data on carbon isotopes from the teeth of 5 other ramidus individuals to conclude that they ate a relatively wide range of plant foods that didn’t include grasses & other savanna plants.

How did this species get arouind its woodland environment? Look at those feet – there’s a sizable gap between the big toe & the rest of the digits, so the foot would have had some ability to grasp branches.However, White et al. also note that the foot had some ‘propulsive capactiy’ ie the individual could also walk bipedaily. Besides that big toe, the forearm:lower leg ratio (similar to that in macaque monkeys, which run along the top of branches) also suggests that ramidus could get around in the trees as well as walk on the ground, as does the structure of the wrist. But there are no adaptations for knuckle-walking – this is significant as we’ve generally thought that the last common ancestor of chimps & hominins was a knuckle-walker. On this basis the authors infer that the gorilla-chimp-human last common ancestor moved around in trees by walking on the tops of branches, and that hominids have never knuckle-walked. This would mean that knuckle-walking & brachiation (swinging along under branches) evolved after the human lineage split from that of the other great apes. And they conclude that

Perhaps the most critical single implication of Ar. ramidus is its reaffirmation of Darwin’s appreciation: Humans did not evolve from chimpanzees but rather through a series of progenitors starting from a distant common ancestor that once occupied the ancient forests of the African Miocene.

 

As you might expect, there’s been a lot of coverage of this by other bloggers: Carl Zimmer’s "Ardipithecus: we meet at last", "At long last, meet Ardipithecus ramidus" by Brian Switek (who provides a very thorough commentary on Ardi’s remains), & "Ardipithecus ramidus" from PZ Myers, to name a few.

 

T.D.White, B.Asfaw, Y.Beyene, Y.Haile-Selassie, C.Owen Lovejoy, G.Suwa & G.WoldeGabriel (2009) Ardipithecus ramidus and the palaeobiology of early hominids. Science 326: 64 (authors’ summary) & 75-86. doi 10.1126/science.1175802

the fabric of history Alison Campbell Oct 02

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Last night I caught parts of Caveman (starring Ringo Starr & a dinosaur) while playing with the puppy – the daughter & her friend were watching it. Um, er, what can I say? …?? I liked the dinosaur, he had personality & panache :-)

Anyway, Ringo & the other human cast members were scurrying around (in a sort of troglodytic way – some of them couldn’t remember whether they were supposed to be bipedal or not….) dressed in fetching ensembles of what may or may not have been faux fur which still allowed them to flash quite a bit of flesh. Archetypical caveman get-up, in other words. We can be fairly sure that our ancestors would have done this, although not when the practice originated – but I’d suspect any naked ape living in a cold climate would have hit on some way of keeping warm, so maybe erectus living in China would have wrapped themselves in animal skins. But when did we become more sophisticated, & develop textiles? A paper published in Science last month suggests that the manufacture of cords from plant material was happening around 30,000 years ago.

In 2007 & 2008 Eliso Kvavadze and his colleagues collected 86 clay samples from the floor of a Georgian cave. During the Upper Palaeolithic the cave was lived in by H.sapiens populations over  some thousands of years. Among the many microfossils contained in the clay (pollen, fungal spores, algae and animal hair), they found hundreds of fibres of wild flax that had been twisted and knotted – & in some cases dyed. While cords made from the fibres could have been used in a variety of ways, the fact that some of them were coloured led the team (Kvavadze et all) to hypothesise that they’d been used to manufacture textiles. While this may sound a bit tenuous, there does seem to be a bit of supporting evidence; the presence of animal hair, the remains of skin beetles (which attack preserved skins) & the spores of a fungus that these days grows on & destroys fabric. So, if this interpretation’s correct (& hopefully there’ll be other, similar finds), then our ancestors were beginning to manufacture textiles not long after they migrated out of Africa & into Georgia around 30,000 years ago.

E.Kvavadze, O.Bar-Josef, A.Belfer-Cohen, E.Boaretto, N.Jakeli, Z.Matskevich & T.Meshveliani (2009) 30,000-year-old wild flax fibres. Science 325: 1359

the fabric of history Alison Campbell Oct 02

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Last night I caught parts of Caveman (starring Ringo Starr & a dinosaur) while playing with the puppy – the daughter & her friend were watching it. Um, er, what can I say? …?? I liked the dinosaur, he had personality & panache :-)

Anyway, Ringo & the other human cast members were scurrying around (in a sort of troglodytic way – some of them couldn’t remember whether they were supposed to be bipedal or not….) dressed in fetching ensembles of what may or may not have been faux fur which still allowed them to flash quite a bit of flesh. Archetypical caveman get-up, in other words. We can be fairly sure that our ancestors would have done this, although not when the practice originated – but I’d suspect any naked ape living in a cold climate would have hit on some way of keeping warm, so maybe erectus living in China would have wrapped themselves in animal skins. But when did we become more sophisticated, & develop textiles? A paper published in Science last month suggests that the manufacture of cords from plant material was happening around 30,000 years ago.

In 2007 & 2008 Eliso Kvavadze and his colleagues collected 86 clay samples from the floor of a Georgian cave. During the Upper Palaeolithic the cave was lived in by H.sapiens populations over  some thousands of years. Among the many microfossils contained in the clay (pollen, fungal spores, algae and animal hair), they found hundreds of fibres of wild flax that had been twisted and knotted – & in some cases dyed. While cords made from the fibres could have been used in a variety of ways, the fact that some of them were coloured led the team (Kvavadze et all) to hypothesise that they’d been used to manufacture textiles. While this may sound a bit tenuous, there does seem to be a bit of supporting evidence; the presence of animal hair, the remains of skin beetles (which attack preserved skins) & the spores of a fungus that these days grows on & destroys fabric. So, if this interpretation’s correct (& hopefully there’ll be other, similar finds), then our ancestors were beginning to manufacture textiles not long after they migrated out of Africa & into Georgia around 30,000 years ago.

E.Kvavadze, O.Bar-Josef, A.Belfer-Cohen, E.Boaretto, N.Jakeli, Z.Matskevich & T.Meshveliani (2009) 30,000-year-old wild flax fibres. Science 325: 1359

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