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Big Brains Require An Explanation, Part II: Sexual Selection, and What Does "Paleolithic" Mean, Anyway?
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February 17, 2012
11:25 pm
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Asclepius:

The article, and the paper it's based on, seem to spend a lot of time dancing around and failing to understand one very simple concept: Prey animals can only adapt in evolutionary time, whereas humans can adapt in cultural time. 

Unfortunately, succinct summations don't get you published.  If you're lucky, they get you quoted (and already being famous helps).

Moving on: trapping is an excellent example of using toolmaking and brainpower to catch prey in an energetically efficient way.  I don't know when the first archaeological evidence of trapping occurs, but I know fishing dates to at least 40 KYA -- and 140 KYA is likely, given the indirect but relatively persuasive evidence at Blombos Cave.

eddie:

Aaron has ably answered the general case, but there are plenty of specific examples.  For example, the aardwolf has become completely insectivorous -- it eats only termites, unlike its carnivorous hyaenid relatives -- and the panda bear, though a true bear of the order Carnivora, subsists entirely on bamboo.  (Though pandas will eat meat and eggs if given to them.)

Aaron:

Hot buttered scorpions...sounds delicious!  I'll take you up on that offer someday, though I won't be as suave about it as this man.

I'd love to have access to the HRAF...maybe someday I'll sign up for the free trial.

Is there still any debate about the monophyletic origin of eukaryotes?  I thought that was a long-settled question...

Asclepius:

I've seen articles which purport to debunk that assertion, but they're based on metrics like rainfall and biomass...so rainforests end up balancing out the desert.  The problem is that the rainforest is a relatively poor environment for biomass edible to humans

There's a reason the American Indians regularly burned off the forest understory and kept the trees thinned...savanna and grassland support lots of tasty grazing animals.  They might have less absolute productivity, but the amount edible to humans is much greater.

vizeet:

"Widespread" is probably an exaggeration, but there is evidence for it in several Paleolithic sites, the earliest dating to 780 KYA.  However, the evidence is not unequivocal until much more recently (AFAIK).

Intra-species competition is a feature of every animal, especially territorial animals (which includes most animals that aren't strict herbivores, for which foliage/grass is nearly everywhere).  The rarer the food source, the more likely intraspecific competition is to exert selection pressure.  Though the direct evidence is thin and speculative, I plan on discussing this.  Thanks for bringing it up!

JS

February 19, 2012
5:38 am
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Gnoll
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"…savanna and grassland support lots of tasty grazing animals…."

 

Not sure if you've read Simon Fairlie's "Meat, A Benign Extravagance" but he makes this point (drawing on the work of Frans Vera) – arguing against the static model of climax vegetation (forest).  One example he gives is when a tree falls in a forest the clearing allows light in that favour grasses and bushes – which encourage herbivores to come in to the clearing and graze.  This grazing and trampling or roots expands the clearing and so you get this ripple-on-a-pond effect where the clearing expands outwards.  Eventually trees recolonise the centre of the clearing, and they themselves expand their territory outwards.

 

Forgive me (yet another) shameless link back to my blog where you can find further detail.  It seems that savanna and grassland are intrinsic to supporting megafauna whereas the 'modern green agenda' seems to favour a 'forests as optimal' policy.  What is 'optimal' is a pulsate, ever-adapting, cyclical model.  There is NO climax to steady state.

 

One other thing that ties this back to your point above, I've read a few books where it is suggested that agriculture is recognisable in some form, long before 10kya.  Slash and burn is one example of how such an agriculture may well manifest.  Rather than being settled agriculture, it has been suggested that humans practiced a kind of stewardship approach to the landscape and the animals upon it. 

 

Not sure if you've read Fairlie's book but I'd highly recommend it and would be interested in your thoughts.

February 20, 2012
8:47 pm
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Asclepius:

You're always welcome to link to relevant posts on your own site.

No, I haven't read Fairlie -- he's "on the list" of books I haven't yet had the time to read -- but that's an excellent point.  In our (justified) zeal to save land from development, we mistake a land depleted of native grazers and covered with climax forest for the "natural" state of the land.

Also, it's true that agriculture wasn't invented overnight.  We have evidence that people were regularly gathering and processing wild grains as early as 19 KYA, at Ohalo II...but it took another 8,000 years before anyone thought to deliberately plow and plant.  And the bone deformities associated with manually grinding sufficient quantities of grain to constitute the majority of the diet only appear after the transition to agriculture (see: Abu Hureyra).

JS

February 20, 2012
10:59 pm
Jeffrey of Troy
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re: rain forest

The Amazon rain forest may not be entirely natural.

Black Gold Of The Amazon

February 21, 2012
12:29 pm
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Jeffrey:

Yes.  That topic is covered at length in 1491, a fascinating book about pre-Columbian civilizations.  Apparently the natives found a way to sustainably farm in the middle of the Amazonian rain forest -- one which has since been lost in a reversion to slash-and-burn techniques.

JS

February 21, 2012
11:50 pm
eddie watts
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well obviously all animals have, but i meant concrete examples in more recent times that we have had a chance to study in any form.

so the answer seems to be not many, and both examples given by J Stanton have moved from a more free dietary choice to a (more) specialised diet.
seems that humans moved to a more freedom of choice diet.

Jeffrey of Troy: that article is a very interesting read thanks!

February 22, 2012
6:20 am
Asclepius
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JS - Not sure if is available to you in the US but if so, it's worth watching,

"In this series Professor Iain Stewart tells a stunning story about our planet. He reveals how the greatest changes to the earth have been driven, above all, by plants.

In the third episode, Iain discovers the remarkable impact of just one plant: grass. On the savannah of South Africa he sees how grass unleashed a firestorm to fight its greatest enemy, the forests. He shows how cutting your finger on a blade of grass shows us how it transformed life in the oceans. In Senegal, he meets the cleverest chimps in the world. And, in the ruins of the oldest temple on Earth, he tells the extraordinary story of how grass triggered human civilisation."

February 23, 2012
12:12 am
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eddie:

Those are just the two examples that came immediately to mind. 

Going the other direction, the spotted hyena's ancestors were most likely pure scavengers, like today's striped and brown hyenas -- but they evolved into fierce and capable hunters without losing their ability to crush and digest bones, or their ability to digest rotten meat that would sicken or kill other predators.

Ravens are another example.  Unfortunately, we don't know much about the ancestors of modern corvids...but since general-purpose intelligence is not a typical feature of birds, it is likely that ravens, which are highly intelligent omnivores, evolved from more specialized ancestors.

Asclepius:

Unfortunately it's blocked outside of the UK -- as are all BBC television programs.  Serves me right for recommending "Ape Genius", which is blocked outside of the US!

JS

February 24, 2012
3:37 am
Grace (Dr.BG)
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Wow Asclepius... I also think of fossil fuels, benzene derivatives and all plastics

February 27, 2012
2:13 pm
Scotlyn
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Ref Wrangham, you are probably right about his work being a mix of science and speculation that requires critical reading, and you are certainly correct that this mix is very entertaining to read. Nevertheless, I believe he is correct to highlight the human propensity to share our food with one another - as opposed to hunting/foraging for oneself and only sharing with any "beggars" one can't shake off - as a dietary habit of humans that, in itself, is as important to explain as any changes in the contents of our diet.

In our (justified) zeal to save land from development, we mistake a land depleted of native grazers and covered with climax forest for the “natural” state of the land.

We've had the opportunity to observe this first hand in Ireland. EU farm policy over the past 30 years has massively incentivised the destocking of grazers on marginal lands, to the point where much of it became covered, not in climax forest, but in impenetrable scrub (gorse) that became a substantial fire risk this past summer.

February 27, 2012
7:54 pm
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Scotlyn:

I think his speculations about the impact of cooking on the human social system are intriguing, and quite possibly correct -- but the evidence so far is that they happened on the currently-accepted timetable for the domestication and usage of fire, not 1.7 MYA as he claims.  You have to throw away a lot of solid evidence, and posit a lot of heretofore-unearthed evidence, to push control of fire back that far.

As I said, the topic deserves an entire article on its own.

Gorse sounds a lot like chaparral, but thornier.  Unfortunately there's a fine line between grazing and overexploitation: you can't simply let cattle loose on a big range and have them do what native grazers did.  You have to confine them to small areas and move them around frequently, to simulate the behavior caused by the predators that aren't chasing them anymore.  Otherwise they just spread out and eat everything down to nubs at once, which isn't good either.

In other words, a true biotic community is a dynamic equilibrium between several opposing forces.  So unless the Irish want to reintroduce wolves and spotted hyenas to Ireland, humans are going to have to engage in active management.

JS

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