Lineweaver on alien human-like intelligence

[GreedyAlgorithm]

Black Belt Bayesian (http://www.acceleratingfuture.com/steven/?p=230) led me to Lineweaver's paper (http://arxiv.org/abs/0711.1751) on oft-neglected aspects of "convergent evolution" and whether alien radio telescopes are as probable as intuition suggests. Spoiler: he claims no. :)

Key teasers which will make you want to read this paper:
We consider ourselves to be the smartest deuterostome. The most intelligent protostome is probably the octopus. After 600 million years of independent evolution and despite their big brains, octopi do not seem to be on the verge of building radio telescopes.

One potential problem with this conclusion: It is possible that existing heads could have suppressed the emergence of subsequent heads. Such suppression would be difficult to establish.

[Cuddles]

whether alien radio telescopes are as probable as intuition suggests.

How probable does intuition suggest they are?

[GreedyAlgorithm]

I'll be more specific:
The comments by Drake (2006) and Sagan (1995b) about the fossil record showing
evidence for a trend toward increasing vertebrate encephalization are references
primarily to the work of paleoneurologist Harry Jerison (Jerison 1973, 1975, 1991).
Lineweaver shows fairly convincingly that the arguments Frank Drake and Carl Sagan used for the likelihood that human-like intelligence will evolve from life given that life exists on a planet are misguided.

In particular, he explores the fact that
When considering convergence, a basic principle is often ignored: the extent of
convergence cannot be larger than the extent of divergence from the common ancestor.
With all terrestrial life having a common origin, one must first quantify the degree of
divergence of two groups before one can discuss their convergence.
If a population of organisms with almost but not quite what we'd call a protobeak produces a population with two distinct types of organisms, each with protobeaks, and then they each evolve beaks, calling that convergent evolution without qualification is misleading.

[INRM]

So it's a fluke that animals have heads? I'm confused, there a LOT of animals on Earth that have heads if not at the very least a centralized nervous system...

[GreedyAlgorithm]

As far as I can gather, he's saying yes, it's entirely possible that heads are a "fluke". See page 9. If the apparatus for easily evolving heads was evolved in organism type X, then anything descended from X which developed a head is not independent evidence for convergent evolution of heads. They're all very tightly correlated, so instead of saying "look at all the animals with heads!" you should say (roughly) "how many pairs of things (extinct or not, doesn't matter) with heads have a nearest common ancestor without a head?", and only use those pairs as evidence for convergent evolution of heads.