How the Brain Evolves

There is even more news upcoming on the Alzheimer's front, for example, some major findings were announced by Stanford University in the area of amyloid plaque; but on that score, we would like to bring you an eyewitness report after we speak to colleagues at Stanford tomorrow.

We would like to offer for thought this important essay on the evolution of the human brain by Dr. Seth Shostak, UC-Berkeley astronomer and SETI Institute scientist.

By Seth Shostak
SETI Institute
posted: 28 October 2004

Is there really life out there? Was a kinder, wetter Mars once dotted by bacterial blooms whose progeny now await our discovery? Do unseen, alien microbes swim in the buried oceans of Europa, Callisto, or Ganymede? What about Titan’s sub-zero methane lakes?

We still don’t know whether any of these nearby worlds houses living things. But the smart money is betting that there are countless alien landscapes, both around our star and others, where conditions are not only ripe for life, but biology has actually burst forth.

The odds for extraterrestrial life, in other words, are reckoned to be good.

But when it comes to intelligent life -- life that could invent science and technology -- the bookmakers hesitate. After all, the road to Homo sapiens was snaky. There were myriad forks in the evolutionary road, and not a few biologists have suggested that if the history of this planet had been only slightly different, humans would never have made the scene. Intelligence was a highly improbable accident, they say.

The only way to thoroughly disprove this rather conservative notion would be to find intelligence elsewhere. That’s what SETI tries to do.

But there’s another line of research that could give us important insights: we could investigate how species become intelligent. If the process that drives species to higher IQ depends on contingency and happenstance, we might infer that thinking is a rare talent. If not, then we can confidently expect plenty of sophisticated galactic brethren.

Regrettably, we still don’t know how our own intelligence arose. What prodded our ancestors to evolve from simple simians to cogitating creatures? One theory says it was all a consequence of mating behavior that selected for reproductive fitness, but there are other possibilities.

As little as we know about our own intellectual history, we know even less about other, clearly brainy species, such as dolphins.

Correction: make that past tense. Some research just published by behavioral biologist Lori Marino (of Emory University and the SETI Insitute), together with her colleagues Dan McShea and Mark D. Uhen, has, for the first time, mapped out the intelligence of toothed whales and dolphins over the past 50 million years. This map may lead us to some real research treasure: uncovering just what it is that provokes evolution to select for high intelligence.

How could Marino and her team measure the IQ’s of animals that breathed their last millions of years ago? She used what has become an accepted standard for gauging the intelligence of animals both dead and alive: the so-called ‘encephalization quotient’, or EQ. Simply put, this is the mass of the brain, as a fraction of body weight. If you have an average-sized brain for your body weight, then your EQ is one. If you have twice as massive a brain as the average species your size, then your EQ is two – and you move, if not to the head of the class, then at least a few rows forward.

For example, cougars, whose body weight is comparable to yours, have EQ’s of one. Humans have an EQ of seven, which means that your brain is roughly seven times more massive than those of these big cats (which is why you can invariably beat them at Scrabble).

Marino’s team spent four years prowling the dusty collections of museums, tracking down fossil crania of toothed whales and dolphins. They then determined their brain volumes with the help of computer tomography. The animals’ weight was estimated by measuring the size of some of the bones where the spinal cord enters the skull, a parameter known to be strongly correlated with body mass. With data in hand, they could then compute the EQ’s of more than 200 specimens, representing 37 families and 62 species.

What did they find? To begin with, cetaceans had a big jump in EQ about 35 million years ago, quadrupling from EQ = 0.5 to EQ = 2.1. No one knows what caused this cerebral shift, but one possibility is that it was the consequence of developing echolocation -- "seeing" their surroundings by voicing high-pitched chirps and analyzing the reflected sounds.

However, in the last 35 million years, these creatures have produced descendants with a wide range of EQ’s, some quite average with EQ’s around 1.0, and others with EQ’s of 4 and 5, rather close to our own. Indeed, as Marino says, "The smarter cetaceans may not be far behind us; they can do a lot of the things that only humans and great apes can do. They might be a good example of a complex, but largely non-technological intelligence."

What does this show? We’re not closely related to dolphins in an evolutionary sense. And yet they developed intelligence comparable to our own. That suggests that there is real survival value in intelligence, and that there are many ways that nature can produce it.

"Here you have four or five different animal groups that, from an evolutionary standpoint, are very different," says Marino. "But there’s clearly a higher order selection effect that has created similarities in function. It might be the consequence of some aspect of social interaction."

"And keep in mind," Marino points out, "brains don’t all just get bigger over time. You’d better have a very good reason for having a big brain, because they’re metabolically very expensive. You’ll have the brain that you need, no more."

But for those creatures inhabiting an ecological niche where intelligence pays off, it sounds as if high IQ’s could be reached via many roads. "Cetaceans and primates are not closely related at all, but both have similar behavior capacities and large brains -- the largest on the planet. Cognitive convergence seems to be the bottom line."

So what about the likelihood of extraterrestrial intelligence? Marino waxes philosophical: "I think this research is a piece of the puzzle, although we still have a long way to go."

"It does tell us something about how intelligence developed on this planet, so the more we learn about that, the better we can estimate the likelihood of it developing elsewhere. And it also gives us a better understanding of what the range of possibilities is."

Humans are not the only brainy game in town. And that statement may extend to the cosmos.

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