Tuesday, April 13, 2010

Which came first? Or, the chicken or egg question is a non-question

There's a commentary by Michael Balter in the April 9 issue of Science, entitled "Did Working Memory Spark Creative Culture?" Did an enhanced ability to remember things make us human?
In the view of Wynn and Coolidge—an archaeologist and a psychologist who form an unusual scientific partnership—a stepwise increase in working memory capacity was central to the evolution of advanced human cognition. They argue that the final steps, consisting of one or more genetic mutations that led to "enhanced working memory," happened sometime after our species appeared nearly 200,000 years ago, and perhaps as recently as 40,000 years ago. With enhanced working memory, modern humans could do what their ancestors could not: express themselves in art and other symbolic behavior, speak in fully grammatical language, plan ahead, and make highly complex tools.
Not everyone is buying this theory, because it's supported by rather sparse data, and because it's not clear which came first, enhanced memory or advanced human cognition, but the theory is making a splash nonetheless.
Despite the critics, Wynn and Coolidge's ideas are increasingly popping up in scientific journals. The pair "have made a really big splash," says Philip Barnard, a cognition researcher at the University of Cambridge in the U.K. This month, Current Anthropology devotes a special online supplement to the topic, and later in April, Wynn and Coolidge will update their ideas at a major meeting on the evolution of language in the Netherlands. The theory makes sense to many. "It is the most impressive, explicit, and scientifically based model" so far, says archaeologist Paul Mellars of the University of Cambridge.

But we aren't here to debate the merits of this theory.  We're here to point out that in a broader, and more serious sense......it's bunkum! Cognition, whatever its molecular and neurobiological nature is, is only one in a long string of human capabilities that have been advocated to be The One that made us what we are.

So, not only our memory, but fire, domesticated dogs, brain size, opposable thumbs, the FOXP2 gene ('for' language), neotenous birth, altered birth canal, the microcephalia gene, among many other traits, behaviors, or genes have been posited as 'the' thing that made us human. Because of natural selection, naturally.

Each of these theories can be backed up by a story that logically (usually) makes sense. Each refers to genuine human traits that are quite different from the corresponding traits in our closest primate relatives. So far so good, and understanding these traits is a fine and important thing to do. But it's curious that each trait is so often just one thing taken in isolation -- and that that one thing is often the researcher's particular area of expertise. 

But, there was no single point in time when we became human. And no single trait evolved in isolation, or simply in response to another. The traits evolved in a higgelty-piggelty way, mosaic changes in varying physical, metabolic, and neurological patterns. Without upright posture, our kind of tool use would not have evolved. That means useful thumbs. Upright posture means various other anatomical changes. Without these, there'd be no need for our kind of brain power. Language, symbolic behavior verbal and otherwise, went hand in hand (or thumb in thumb?) with these other changes.  This is what's interesting about how evolution works.  The fact that everything evolves together -- must co-evolve -- which of course is true of every species, not just humans.  Even if something like the enhanced memory theory "makes sense to many", it's nonsense to treat these traits in isolation.  

And, evolution doesn't work by leaps, which is what most of these theories in effect would require: A point in time when a new thumb form or a tame wolf was enough to allow its owner to have more children than those in his or her small band who were less well-endowed, a kind of luck that would have had to carry on for many generations. All the kinds of traits that are posited as the one that made us human are complex, they evolved slowly over many millennia, and they generally arose together. The idea that we should be able to attribute our "humanness" to a single gene or trait -- a kind of 'Master' trait, which would have had to precede the others -- involves precisely the same determinism and darwinian fundamentalism that we so frequently criticize. 

It was long ago -- in 1929 -- when the Taung specimen was unearthed in South Africa. That specimen showed that, contrary to our egotistical preconceptions, the noble (gratuitously greedy and murderous?) human brain, did not lead the way. Upright posture of a sort evolved first. Culture evolved along the way, bit by bit, and does not require a huge brain per se. Trying to hawk MyFavoriteTrait is good for making a news splash, but is misleading science. Fortunately, while it helps build careers, most of the nonsensical aspects quickly fade. Meanwhile, those who are serious about human evolution can ignore the carnival barking and study the traits in a more sober evolutionary sense.

11 comments:

Holly Dunsworth said...

The egg IS a chicken.

Ken Weiss said...

Yes, and chickens are just continuation of chicken-cells all the way back to Ur-chicken, the AdamEve of chickens, which of course is just a continuation of bird-cells,etc.

They are obviously the same because you can also fry a chicken as well as an egg. You can have a chicken or an egg sandwich.

But there is a difference. I know what an egg over easy is, but...

Sam said...

Holly, that sounds like fodder for pro-lifers. Ken, not so much.

Anne Buchanan said...

Sam, I thought they were both making a strong argument pro vegan.

Ken Weiss said...

Well, the truth is that if a egg is a chicken, which it certainly is in the biological sense, so is an embryo.

The pro-life/pro-choice debate is only properly viewed as an anthropological one about defining what 'counts' as human life, a cultural issue not a biological one.

James Goetz said...

Hi Ken and Anne,

This blog makes you guys more prolific than I ever imagined.:)

Anyway, per your post, I suppose part of the problem is that this has nothing to do with the origin of species, but only the origin of traits. And in the case of "thinking related traits," specimens could have a thinking related trait with no outward evidence of it. For example, I suppose we can safely assume that many humans for thousands of years had the nervous system hardware to do calculus before Leibniz and Newton discovered calculus. And there was no outward evidence of this until Leibniz and Newton discovered calculus.

I am interested in the origin of abstract thinking, which is needed for both scientific theory and religious experiences. Regardless of the nebulousness of defining the origin of Homo sapiens, I hold that abstract thinking defines humanity. I also understand that this has caveats. For example, perhaps at least some infants might have died before developing abstract thoughts. And perhaps some congenital disorders prevented some humans from developing abstract thoughts even in adulthood. (This is my educated guess.)

In general, I assume that a particular genotype caused the origin of nervous system hardware in a hominid specimen. The parents of this hominid were close to having the nervous system hardware for abstract thinking, but fell short of it by a "straw." Then originated the germ-line "genotypic straw that broke the camels back" while the first hominid developed nervous system hardware capable of abstract thought. Others in the same population around the same time might have been born with the same trait. And hominids with the "abstract thought trait" would have siblings and without the trait. And unless the trait was homozygotic and included a strong mating selection, then some children of the hominids with the abstract thought trait would not have the trait. And the first hominids with the abstract thought trait would have been nurtured by parents without the trait, which could have slowed down the outward evidence of the trait.

By the way, I have little idea when this scenario happened or what it would take to figure out when it happened give or take a few thousand years.:) And I hope you could follow what I summarized above.:)

Ken Weiss said...

The basic argument is not new. Wallace thought humans needed divine assistance because of the calculus kind of reasoning. Your idea that it is abstract reasoning (or something of that sort), not calculus per se, is the obvious answer.

However, it would almost certainly not be a mutation in one gene, or suddenly arise and then persist. It would come on gradually over many many generations with many genes contributing and gradually attain its current state, in which there is variation in the nature of each of our 'abstract reasoning' abilities (that's of course hard even to define). However natural selection were involved, it would work on the net ability, not the specific gene.

Speciation and adaptation may be correlated but they are not the same. That's not widely appreciated, because the usual Darwinian explanation is that after a lot of separation time, different adaptations occur in different isolated populations, and this leads to them evolving into different species. But diverse adaptations don't imply mating barriers (species formation) and mating barriers can be created by single mutations (examples are known) with no other adaptations.

James Goetz said...

I'll clarify two things. First, my statement about abstract thought defining humanity isn't a scientific statement but a philosophical statement. Second, I made no suggestion about divine assistance but that various nervous system adaptations in humans enabled both religious experiences and the development of scientific theories (see Newberg and D'Aquili).

Ken Weiss said...

Yes, that's what I thought. First, I'd say the definition of humans as the 'rational animal' (goes back to Aristotle) is perfectly OK to do, since definitions are arbitrary.

But it can be misleading. What about, say, Neanderthals. It would be hard to state that they weren't rational. As an evolutionary biologist I'd say that other animals, maybe much more divergent from us than we like to fancy, are capable of abstract thought. But that, again, may be a matter of definition.

I would agree that whatever gave us (or whoever before us in our ancestry) the power of abstract thought it would not be related to math or poetry, but other things, like imagining where prey might be without having to smell them, etc.

Of course, I'd b the last to deny the reasonableness of philosophical statements or approaches to life!

James Goetz said...

Yes, the origin of "abstract thought adaptations" presumably helped with hunting and defense against lions and other dangerous animals while the byproducts of those adaptions included poetry and math.

James Goetz said...

And concerning Neanderthals, I suppose that anthropologists have yet to unequivocally classify them as Homo neanderthalensis while there's some chance that they're H. sapiens neanderthalensis. And I admit that I get dizzied trying to follow the last 25 years of related discoveries and scientific bickering.:)