Monday, January 29, 2007

Evolution has halted

In one of his books (The Story of B maybe?), Quinn said that we have halted evolution.  He only mentioned the idea in passing, and it hasn't reappeared in other books, so I'm guessing he doesn't consider it a key element of his ideas.  Still, it is one that caught my attention. What does he mean?
Modern medicine and friends
I've heard people say something like this before, but usually it turns out that they just don't understand what evolution is.  They typically mean something like 
In the 'wild', people who (can't see / can't walk / have regular seizures / have acute ashma / have low sperm counts / etc.) would not survive to reproduce, thus the human species would tend to select for the opposite traits.  Thanks to modern medicine we allow these traits to continue to occur, and potentially proliferate in our gene pool, resulting in a weaker human population over time.

Or to put it colloquially, "our technology means that the human species is getting worse."  (The problem with that statement, of course, is that evolution doesn't say anything about "better" or "worse" but merely about "more fit" and "less fit" to survive in a given niche.)
I don't disagree that this occurs.  In fact, I have an example that is close to home.  My English grandfather was not sent off to fight in World War II, because he had asthma.  While his healthier peers went off & died, he stayed home and had 3 children, all of whom had some breathing issues.  I have some of those traits, albeit mild ones.  The decision to select non-asthmatics as soldiers meant that we selected for asthma in the next generation of the English.
However, this doesn't mean that evolution has halted.  It means that the mechanism of selection has changed.  In a hunter-gatherer tribe, the ability to, well, hunt and gather, is clearly critical to survival, so characteristics that interfere with the ability to do those things ( e.g. blindness) are likely to reduce reproduction, and hence their representation in the gene pool.  In modern, civilized society, the criteria are different, but they still exist.  For example, physical attractiveness is still a factor in sexual selection; the ability to eliminate or tolerate certain toxins (e.g., cadmium, mercury) or radiation is more important today than it was 10,000 years ago.  So, evolution of humans still occurs today, and will always occur.
Similarly, the characteristics that are selected for in other species have been dramatically affected by the world-wide dominance of human civilization.  The traits of cows are desirable to humans as a food source, so we increase their opportunity to proliferate.  Meanwhile, predators of cows, such as wolves, have traits that interfere with cow's proliferation, so we reduce their opportunity to proliferate.  In these ways, we have a dramatic impact on the gene pools of both cows and wolves on the earth.
Now, I don't know for sure what Quinn meant, but I'm guessing this isn't it.  He clearly has a deep understanding of evolution and natural selection -- probably much deeper than mine -- so he probably wouldn't make such a simple error.
Food supply limitations
Perhaps what Quinn meant was:
Consider that civilized humans transform available land from its wild state to a food-producing state.  We do this rapidly and efficiently, thereby allowing us to produce corresponding increases in food supply.  Whereas non-civilized peoples have allowed food supply to limit their numbers ("living in the hands of the gods"), we have effectively removed the limits on food availability for nearly all humans on earth.  In this way, a limited food supply is not a significant factor in the gene selection of civilized people.
That seems much more reasonable, and in line with a lot of what Quinn has to say elsewhere, but I still have trouble believing that's what he meant.  Saying that you have "stopped evolution" seems to be a much stronger statement than saying that you have "removed food supply limitations as an environmental selector".
Who lives and who dies?
Or perhaps he meant:
Consider that civilized humans will, without hestiation, obliterate obstacles to increasing food supply for humans.  Cows like to graze pasture, so we'll destroy rain forests extremely rapidly ( 100 acres / minute!), destorying the "inconsequential" life in that area, so that our cows may graze.  If wolves show interest in our cows, we won't just defend the cows when the wolves approach.  We systematically seek out and destroy all wolves, nearly eliminating them as a species, on purpose.  We make the decisions about which species thrive and which are decimated.  For millions of years, the selection was made by a complex mix of natural forces; for the past 10,000 years, we have taken that decision in to our own hands.  We decide who lives and who dies.
The gods love diversity
Or perhaps even:
The universe if full of diversity.  Each blade of grass is unique.  Each plant is unique.  Each mammal is unique.  Each species is unique.  Just as the Law of Gravity is written in every particle of matter, the Law of Life is written in every living thing.  Diversity of life is at the essense of that law.  Diversity of life is at the essense of the theory of natural selection.  Civilized man has dramatically reduced the diversity of life on the earth, by driving some species to extinction, while we allow others to proliferate almost unchecked.  The result dismantles the normal functioning of evolution by natural selection.
It's just selection
Maybe it's something much simpler.  Wikipedia's summary of Darwin's theory is "populations evolve over the course of generations through a process of natural selection".  Under natural selection, it says:

Natural selection is the process by which favorable traits that are heritable propagate throughout a reproductive population: individual organisms with favorable traits are more likely to survive and reproduce than those with unfavorable traits. If these traits have a genetic basis, then the genotypes associated with the favored traits will increase in frequency in the next generation. Given enough time, this passive process results in adaptations and speciation (see evolution). Natural selection explains why living creatures seem to match their environmental niches so well.

Natural selection is one of the cornerstones of modern biology. The term was introduced by Charles Darwin in his groundbreaking 1859 book The Origin of Species, [1] by analogy with artificial selection, by which a farmer selects his breeding stock.

So, maybe Quinn means "we've stopped evolution by replacing natural selection with artificial selection".
Hmm.  This last one seems the most plausible -- it's the one that holds together, and the one that you'd expect from someone who had studied evolution carefully.

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