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Big Brains Require An Explanation, Part II: Sexual Selection, and What Does "Paleolithic" Mean, Anyway?
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February 15, 2012
5:00 am
First-Eater
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Upon writing Part I of this article, it expanded to two parts...and now it's expanded to three parts! So if an issue you were hoping to learn about hasn't yet been covered, rest assured I'll get to it.

(Or, go back to Part I.)

Let's Get Oriented In Time: What Does "Paleolithic" Mean?

Since we've talking about the for years, and this series explores the increased brain size and behavioral complexity that took place during the Paleolithic, I think it's important to understand exactly what the term "Paleolithic" means. Yes, everyone knows that it happened a long time ago—but…

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February 15, 2012
5:53 am
Asclepius
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In the course of evolution a good 'invention' is quickly spread and can arise independently several times. I've read that the pre-Cambrian explosion may well have been driven by the 'development' of the eye, prior to which the main senses were smell, vibration, and touch.

An eye allows you to plan well ahead - you get much more information from an image than via other senses (eg. not only the size of a predator/prey but also vector information - is it coming towards me? Is it a threat? And we are all aware how much of communication is non-verbal).

I'm suspecting that your theory for an increase in brain size is moving towards the notion of 'fugitive calories' and an environment dominated by physically superior predators that we learned to outwit.

An 'eye' might let you see ahead over the next rendezvous with a predator/prey, but a brain lets you plan ahead over days, weeks and years. With ingenuity you can outwit the biggest, strongest and fastest animals and you can also get around chemical defense (fermenting and cooking are examples of this).

I'm still sold on the importance of sexual selection, but am looking forwards to the next installment to be convinced otherwise!

It is interesting to note that the human brain still has a reptillian brain at it core. Through the sieve of evolution we just added on to it.

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February 15, 2012
6:30 am
anand srivastava
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What about the gatherer? Aren't they supposed to collect tubers and fruits wherever available. Those IMO would be in most places in Africa even during cold times. What about Turkana basin which is supposed to have been warm for at least the last 4 million years, and is supposed to be the cradle of humanity, and gave us our lack of fur and high sweat glands?

According to Wrangham, cooking must have divided us into hunters and gatherers. Also the fact is that hunting is hard, and is not successful all the time. There would need to be an alternate food for the times it fails. Humans couldn't be just starving like carnivores, when our body can digest carbs, and there is plentiful carbs around as tubers.

The other issue is that during low vegetation periods, animals become very lean, and not really useful for eating, unless supported by tubers. Its not like every tribe was able to do things done by the native americans.

Could it be that we are seeing only one side of the story?

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February 15, 2012
10:16 am
Andrea Reina
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I don't think J means to discount tubers and other starchy plant foods as fuel sources during the paleolithic, just that in the context of mate selection there's a much bigger difference between a good hunter and a bad hunter, and a good gatherer and a bad gatherer. If I knew what to look for I would do a decent job of collecting tubers, fruits, edible leaves, etc. Give me a spear and point me at a herd of, well, anything, and I'd probably be lucky to escape without a self-inflicted wound. And J does include tubers and other non-seed glucose sources in "Eat Like A Predator".

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February 15, 2012
12:53 pm
Beth
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Off the wall question: If a person were to meet J IRL & then describe this person to others, would the pronoun be "he" or "she"? That is, is JS of the male or female persuasion?

It's not important, but I am curious. I hear the words coming from JS in a female voice, but I see that others refer to J as "he".

Beth

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February 15, 2012
1:43 pm
Grace (Dr.BG)
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Very nice!!!!! I'm glad you conceded to include sexual selection's mark on the evolution of the brain. I concur with Asclepius' comments (and past ones)!

So... My question. *haaaa aahh* If we outwit, outplay and outseduce our predators and partners, then are our big brains the bigger gonads?!???

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February 15, 2012
1:53 pm
Grace (Dr.BG)
Guest

I like the reasoning here btw...

Out hunt/Out forage = Out feed = Out breed

AAAaaahhhhh ha (unfortunately this applies also to modern refined high energy food sources and the legion of bottom feeders created who fail to fully utilize their big phat brains)

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February 15, 2012
7:21 pm
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February 22, 2010
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Asclepius:

General-purpose intelligence has arisen many times in the animal kingdom.  Even sufficient abstraction and dexterity to make and use tools has been demonstrated by birds as well as primates.  The question we must always ask is "to what survival advantage?"

And yes, the human brain is absolutely a big layer cake, with the forebrain being a thin layer of rationality grafted onto hundreds of millions of years of 'instinct'.

Andrea:

Exactly.  Whether we ate a food isn't the same as claiming that it exerted significant selection pressure.  For example, humans eat fruit, but so do bats, monkeys, and almost everything that can get to them...it's difficult to argue that frugivory requires big brains.

anand:

Gathering is absolutely an important source of calories...but see my reply to Andrea above.  Like I said, I'll get to Wrangham soon.  (Next week, unless another intermediate topic expands greatly.)

Beth:

I try to keep the focus on the science, not on myself...thus the lack of self-portraits or biography.

Dr. BG:

As I said in the article, I find sexual selection both important and fascinating!  In this particular case, the evidence is that sexual selection was providing the same pressures as natural selection -- so we don't need to invoke it separately in order to explain the existence of big brains.  However, I believe it's probably the most parsimonious explanation for some of the things we've done with those big brains since we got them!

Big brains are gonads for memes.  That's a meme, btw.

And your final point is excellent.  Natural selection doesn't care if you're healthy or happy: it's a statement of fact about which genes are surviving and propagating to subsequent generations.

 

Thanks again for the perceptive comments, everyone!  I appreciate your patience with these stage-setting articles...we'll be enjoying some conclusions soon.

JS

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February 15, 2012
9:50 pm
vizeet
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I think it is important that blog mentions the difference between human and our primates in terms of evolution of brain.
This will help me better understand evolution.
I assume since homoerectus were doing more scavanging and hunting then its primates he required certain physical features:
1. Running away fast
2. Seeing predators from distance
3. Need to have better co-ordination
Just like spotted hyena.
High fat from bone marrow and brain helped simplify gut so he could stand straight. Also humans are taller then our primates which might also have helped in seeing predators early.
Also Homo Erectus also moved out of Africa just like human ancestors. There should be a strong reason why this happened.

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February 16, 2012
12:24 am
First-Eater
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February 22, 2010
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vizeet:

The consensus narrative has undergone several revisions as we discover more fossil hominids from the Pliocene.  I'll make sure to summarize it next week.

Interestingly, spotted hyenas are most likely descended from scavenger ancestors, but developed into strong hunters as they speciated (while keeping their bone-crushing abilities and ability to eat rotten meat).  Brown and striped hyenas are still nearly 100% scavengers.

You raise a great point, which I plan on discussing: the Homo Erectus migration out of Africa demands an explanation.  What adaptations allowed Homo erectus to travel and survive outside of Africa?  And why were they supplanted by the later migration of Homo sapiens?

JS

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February 16, 2012
2:17 pm
Scotlyn
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Since it's been mentioned several times, here are a couple of things I remember from "Catching Fire" by R. Wrangham, which I found absolutely fascinating.
1) the differences between chimp hunting and human hunting.
a. chimps spend, at most, around 20 minutes on any individual hunt, this being the longest they can manage to free up enough time and energy from the endless round of chewing their food (5-7 hours per day) that is necessary for them. If they don't catch their prey within this timeframe they give up. Humans go on lengthy hunts, sometimes lasting many hours to days, and on their return need to have a meal ready for them that can be quickly consumed (cooked food meets this need), often in the dark (the fire that cooked the food, also provides enough light to see what you're eating).
b. chimp males hunt, chimp females not so much. The males seldom share, although sometimes they may reward a persistent female or juvenile "beggar," meaning females and juveniles eat much less meat than males. In humans, the meat hunted is shared, sometimes with extreme attention to providing equal shares, with everyone within the band, family or locality. There is little discernible difference between female and male or adult and juvenile meat consumption.

2) This food sharing between the different sexes, and all ages, is the singular human "fact" that Wrangham stresses as making humans different, and argues that it is difficult to conceive of in a context with no cooking, as raw food is time-consuming to eat, and frees up little time for other activities, especially human style extended hunting activities. Hunting AND gathering, as a way of life, implies some specialisation in the methods of obtaining foods, as well as a common base to which all foods are brought for sharing so that everyone benefits from the same diet combining the different specialised activities. Human hunters, in Wrangham's view, may or may not require gatherers (eg Inuit and other almost exclusively meat-eating cultures), but definitely do require cooks. Likewise cooks, require protection for their kitchen stores and fires from food thieves. Wrangham gets to the beginning of a very interesting line of thought about human gender relations with this argument.

There is more, but this is a taste of a book that leaves the reader with a great deal to think about for long after.

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February 16, 2012
2:59 pm
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February 22, 2010
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Scotlyn:

I'll get to Wrangham next week, but in the meantime: be very careful to read him critically.  His writing is a mix of real science, entertaining speculation, selective citation, and interpretations completely at odds with the rest of the scientific community (and, often, the evidence) stated as incontrovertible fact.

In other words, he tells a great story…but it's not necessarily true.

"chimps spend, at most, around 20 minutes on any individual hunt"

This is because monkeys are small and the energy cost of chasing monkeys up trees is very high — and it is therefore energetically counterproductive to spend too much time chasing them.  (See the extensive calculations in Boesch 1994.)  In contrast, human hunters prey on much larger animals, for which a much longer chase is still energetically profitable, and we do so in a much less energy-intensive way (walking or running on open ground).

I find it bizarre that Wrangham would bypass this basic fact (in a paper by a fellow chimpanzee researcher with whom he cannot fail to be familiar) in favor of the needlessly complicated hypothesis he proposes.

"Human hunters, in Wrangham's view, may or may not require gatherers (eg Inuit and other almost exclusively meat-eating cultures), but definitely do require cooks."

Another false statement.  Humans have no trouble digesting raw meat.  (You can ask Lex Rooker or Peggy the Primal Parent about that…both have lived for extended periods entirely on raw meat.)  It's certainly quicker to chew cooked meat…but when we're talking about something with the energy density of meat and fat, it's not a limiting factor.

What this is telling me is that I need to write an entire article just on that book!  It won't be part of this series, though, because many of these points aren't directly germane to the topic at hand.

JS

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February 16, 2012
10:58 pm
aaron blaisdell
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Let's not forget that gathering included not only plants but many animals, too, both invertebrate (snails, grubs, shell fish) and vertabrate (lizards, turtles, etc.) alike.

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February 17, 2012
1:13 am
First-Eater
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February 22, 2010
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Aaron:

Absolutely true!  Furthermore, much of the animal protein that was gathered is in forms we don't eat in the Western world (e.g. insects, grubs).

If I recall correctly, this dietary shift has been a source of confusion in the past when arguing about hunter-gather dietary composition.  From the modern viewpoint, calories from "gathering activities" would have to be exclusively carbohydrate from plants...but that's clearly not the case.

I'm doing my best to stick to the narrative...but the implications of all these facts could easily support an entire book.  At least I'm in no danger of running out of topics to write about!

JS

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February 17, 2012
2:21 am
Asclepius
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February 17, 2012
4:10 am
Asclepius
Guest

"This is because monkeys are small and the energy cost of chasing monkeys up trees is very high — and it is therefore energetically counterproductive to spend too much time chasing them. (See the extensive calculations in Boesch 1994.) In contrast, human hunters prey on much larger animals, for which a much longer chase is still energetically profitable, and we do so in a much less energy-intensive way (walking or running on open ground)."

A great point. Furthermore humans are ingenious enough to set traps. One of man's most sedate activities is a form of hunting; fishing! I recall seening Africans hunting monkeys simply by putting treats in holes deep in rocks. The monkeys - ever curious - reach in to grab the treat, but their fist traps them. They will not release the treat to get their hand out even though the hunter walks towards them to kill them. There are sites in the UK where we see evidence of mammoth being scared by hunters to run over cliffs (we assume fire was used to do this). The base of the cliffs show much evidence of butchery. Also we have long range weapons.

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February 17, 2012
6:03 am
eddie watts
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something that interests me a great deal is whether humans are the only animal which has ever changed it's dietary source, this assuming we did come from small ape-like creatures which largely ate plants.

looking forward to the rest of the series!

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February 17, 2012
8:44 am
Aaron Blaisdell
Guest

@Eddie Watts. Well, think about it this way. If every extant (currently living) species on earth is the descendant of a long lineage of ancestors traced all the way back to the first prokaryote (simple, single-celled organism) circa 3.5 bya (J hasn't defined this acronym, but it means "billion years ago"), then EVERY extinct and extant species that ever lived on the planet has changed its dietary source. This must be the case if you accept that all life on Earth is monophyletic in its origins.

@J, yes, the hraf (human relations area file, which is a database of ethnographies with searchable keywords–a fascinating place in which to lose yourself!) generally classifies the collection of bugs, worms, snails, etc. as gathering, not hunting. Thus, estimates of the ratio of plant (obviously gathered) to animal (hunted AND gathered) sources of contemporary or recent hunter gatherer diets is biased towards the plant side if gathering is interpreted to only mean plant materials. This is the problem with using terms like "hunting" and "gathering" as proxies for animal and plant consumption, respectively.

JS, next time your in LA, I'll take you to the Santa Monica airport at which there is a nice restaurant called Typhoon. They have an invertebrate section on their menu that includes scorpions (quite crunchy!, served on toast, but you can ditch the toast), fried crickets, Vietnamese waterbugs, etc.

Btw, when I first met JS at AHS11, my first thought was "he sure looks like a gnoll!". By the way, male and female hyenas can be difficult to tell apart due to the androphication (is that a word?) of the females, including some of their, ahem, crotch anatomy.

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February 17, 2012
10:00 am
Asclepius
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@Aaron Blaisdell – "when I first met JS at AHS11, my first thought was “he sure looks like a gnoll!”." That made me smile.

– ——
One thing that stikes me about modern HG commentary is that it often fails to note that many of the HGs that have been studied are surviving in arguably marginal conditions – either pushed out by agriculture and colonialism to remote land (which is impoverished as the most fertile land was taken for farming), and, is existing in a post-megafauna age.

The geographic distribution of HG would have varied massively over the past 2my. Where HG have thrived/prefer to exist and where they are now found are not necessarily the same thing. Also, we might see HG hunting birds in the Savannah – but if they could hunt something much bigger and juicier, I am sure they would do! We should not confuse 'optimal/preferred behaviour' with 'survival bahviour'.

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February 17, 2012
11:50 am
Vizeet
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I think that Homo-Erectus lived in small groups and there were frequent clashes between these groups. I read somewhere that cannibalism was wide-spread in early paleolithic and it did existed until recently (though insignificant). In such condition surviving will need following traits:
1. Intelligence (Strength is less important because others are almost as strong)
2. Communication (Which might have caused development of verbal ability)
3. Learning
4. Co-ordination
So humans ancestors were competing with each other for survival.

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