Myth number one: To say that there’s in some sense a “higher purpose” means there are “spooky forces” at work.

When I ask scientifically minded people if they think life on earth may have some larger purpose, they typically say no. If I ask them to explain their view, it often turns out that they think that answering yes would mean departing from a scientific worldview — embracing the possibility of supernatural beings or, at the very least, of immaterial factors that lie beyond scientific measurement. But Hamilton’s thought experiment shows that this isn’t necessarily so.

You may consider aliens spooky, but they’re not a spooky force. And they’re not supernatural beings. They’re just physical beings, like us. Their technology is so advanced that their interventions might seem miraculous to us — as various smartphone apps would seem to my great-, great-grandparents — but these interventions would in fact comply with the laws of science.

More to the point: If you ask how Hamilton’s aliens had initially imparted “purpose” to life, the answer is that they did so in concrete fashion: by planting simple self-replicating material on earth a few billion years ago, confident that it would lead to something that would keep them entertained (keeping them entertained being, in this scenario, life’s purpose). Which leads to:

Myth number two: To say that evolution has a purpose is to say that it is driven by something other than natural selection.

The correction of this misconception is in some ways just a corollary of the correction of the first misconception, but it’s worth spelling out: Evolution can have a purpose even if it is a wholly mechanical, material process — that is, even if its sole engine is natural selection. After all, clocks have purposes — to keep time, a purpose imparted by clockmakers — and they’re wholly mechanical. Of course, to suggest that evolution involves the unfolding of some purpose is to suggest that evolution has in some sense been heading somewhere — namely, toward the realization of its purpose. Which leads to:

Myth number three: Evolution couldn’t have a purpose, because it doesn’t have a direction.

The idea that evolution is fundamentally directionless is widespread, in part because one great popularizer of evolution, Stephen Jay Gould, worked hard to leave that impression. As I and others have argued, Gould was at best misleading on this point. And, anyway, even Gould admitted that, yes, on balance evolution tends to create beings of greater and greater complexity. A number of evolutionary biologists would go further and say that evolution was likely, given long enough, to create animals as intelligent as us.

In fact, that idea is implicit in Hamilton’s saying the aliens could have “set up” evolution in such a way that “it would produce these really interesting characters — humans.” This part of Hamilton’s scenario requires no intervention on the part of the aliens, because he believed that evolution by natural selection has a kind of direction in the sense that it is likely, given long enough, to produce very intelligent forms of life. (When speaking more precisely, as he did in other parts of the interview, Hamilton would say that the human species per se wasn’t in the cards — that it wasn’t inevitable that the first intelligent species would look like us.)