Wednesday, October 25, 2006

ET and the Evolution of Intelligence

A very interesting post from PZ Myers today at Pharyungula on the likelihood of ET existing and the evolution of intelligence.

Firstly, the Drake Equation and Fermi Paradox. The Drake Equation states that:

N = R* × f{p} × n{e} × f{l} × f{i} × f{c} × L

N is the number of civilizations in our galaxy with which we might expect to be able to communicate at any given time

R* is the rate of star formation in our galaxy
f{p} is the fraction of those stars that have planets
n{e} is average number of planets that can potentially support life per star that has planets
f{l} is the fraction of the above that actually go on to develop life
f{i} is the fraction of the above that actually go on to develop intelligent life
f{c} is the fraction of the above that are willing and able to communicate
L is the expected lifetime of such a civilization

Briefly, when “plausible” were values plugged into the Drake equation, values for N were usually greater than one (i.e. we aren’t alone). The Fermi paradox is that, to our knowledge, N=1, when really we should have seen other civilizations by now.

So what’s wrong?

According to Myers:

I think it's a non-problem and a non-paradox. The simplest explanation for the reason that ET isn't tapping on our shoulder is that the Fermi and Drake assumptions are wrong—the kind of technological intelligence that might build spaceships and radios and harness fire is very rare, and techno-species are spread very thinly over vast and uncrossable tracts of space.
And why is ET intelligent enough?

………… we do have one fairly substantial body of evidence that illustrates the probability of intelligence evolving, and it's right here in the history of planet earth. We've got about a half-billion years worth of sophisticated multi-cellular animal life on the planet, and our kind of technological intelligence has appeared only once. From the Planetary Society debate on SETI:

After the origin of life, that is, 3.8 billion years ago, life on Earth consisted for 2 billion years only of simple prokaryotes, cells without an organized nucleus. These bacteria and their relatives developed surely 50 to 100 different (some perhaps very different) lineages, but, in this enormously long time, none of them led to intelligence. Owing to an astonishing, unique event that is even today only partially explained, about 1,800 million years ago the first eukaryote originated, a creature with a well organized nucleus and the other characteristics of "higher" organisms. From the rich world of the protists (consisting of only a single cell) there eventually originated three groups of multicellular organisms: fungi, plants and animals. But none of the millions of species of fungi and plants was able to produce intelligence.

The animals (Metazoa) branched out in the Precambrian and Cambrian time periods to about 60 to 80 lineages (phyla). Only a single one of them, that of the chordates, led eventually to genuine intelligence. The chordates are an old and well diversified group, but only one of its numerous lineages, that of the vertebrates, eventually produced intelligence. Among the vertebrates, a whole series of groups evolved--types of fishes, amphibians, reptiles, birds and mammals. Again only a single lineage, that of the mammals, led to high intelligence. The mammals had a long evolutionary history which began in the Triassic Period, more than 200 million years ago, but only in the latter part of the Tertiary Period--that is, some 15 to 20 million years ago--did higher intelligence originate in one of the circa 24 orders of mammals.

The elaboration of the brain of the hominids began less than 3 million years ago, and that of the cortex of Homo sapiens occurred only about 300,000 years ago. Nothing demonstrates the improbability of the origin of high intelligence better than the millions of phyletic lineages that failed to achieve it.

In part, this is a probability argument: it is saying that the relevant parameter in the Drake Equation is very, very small, perhaps much smaller than the SETI devotees were plugging into it. Maybe, if we actually had accurate values for the equation, the expected number of space-faring civilizations in our galaxy is something less than 1. The 'paradox' isn't.

Myers then goes on to say:

But there's another, subtler lesson in there. What he's saying is that there doesn't seem to be any evidence for a predisposition to favor intelligence in biology. Features like multi-cellularity, photoreception, long sharp fangs, flight, etc., pop up in life's history over and over again, independently; but intelligence? Feh. The universe doesn't seem to like smart guys. We happened once, and what's more, we seem to be teetering at the end of one long chain of improbable events in the history of one marginal set of lineages, of which most of its members are in decline.

Now, I’m not sure if you can extrapolate from this argument to cover other parts of the universe, with the reason being that our planetary conditions may be great for the development of life but poor for the development of intelligence.

Continual environmental upheaval would appear to be a likely reason that life that is similarly intelligent to humans is rather uncommon. The costs of
developing intelligence in a continuously changing environment could easily lead to reduced physical adaptability, which just isn’t compensated for. Something as complex and finely tuned as the human brain, for example, has very, very specific requirements as far as oxygen, temperature and sustenance requirements etcetera are concerned. Complex brains need more time to develop and mature then less complex ones. This very complexity makes them fragile, meaning a complex brain is mostly selected against when the environment changes (luckily our lineage was an exception).

However, in a more stable environment, intelligence would have more positive aspects and less negative ones. The balance would tip further toward an ecological evolutionary driving force (e.g. predator/prey interactions), rather than an environmental ones (eg. abiotic stress tolerance). Intelligence would certainly help the former example but not the latter.

So, I tend to think that the predisposition for the development of intelligent life is there, providing a largely stable environment is present. And one thing we just don’t know at all is how many planets exist with stable environments. Maybe none. Maybe lots.