The Great Filter

Robin Hanson (
Mon, 2 Sep 96 14:08:43 PDT

Eric Watt Forste writes:
>>As Nicholas said, its implausible that a very hard step, such as
>>language, happened so soon after its enabling large brains prior step,
>>unless some special very usual environment was involved (and its hard
>>to see what that could be).
>In that case, I suppose that evidence for language use among pongids and
>cetaceans would strengthen the argument for identifying the bulk of the
>Filter with the development of linguistic ability, would it not?

Do you mean that a potential for language ability developed long ago,
and just flowered "recently" as brains got big?

>One thing about birds is that they have wings, and so most of them have
>strong selective pressure favoring flight, which selects against large
>brains. ... These two
>factors might be enough to keep the birds "Filtered" out for at least a few
>million more years even if their brains have the same neurostructural basis
>necessary for the ultimate development of language use.

The question is: had there not been mammals around when the dinos were
wiped out, could the birds have radiated to fill the gap, and followed
a similar trajectory to our position within a hundred million years?
If yes, this is not a hard step.

Johh Clark writes:
>I don't think the key step was making the first tool, it was making the first
>hand that could make the first tool, and I don't think brain growth was
>steady, it took an enormous spurt as soon as that first hand came into
>existence. ... 1) Why did bipedalism develop?

If hands were so hard, why did they happen so soon after brains were
near ready to use them? Or ask the same question about bipedalism.
And if you take a long view, graphing encephalization on a log plot
over a hundred million years, growth really is roughly steady since
the dinos were killed.

Sean Morgan writes:
>There an article in _Analog_ a several years ago called "The Long Stern
>Chase" (I forget the author) which suggested that the capacity to sweat is a
>filter too [pardon the repetition if I wrote about this here before]. It's

Without big brains, the ability to sweat probably wouldn't have got us
far. So the hard thing to understand is, if sweating is so hard, why
did it happen so fast after the big brains arrived?

Robin Hanson