At last, a reply to the interesting stuff! :)
IIRC myelinated neurons are both more energy efficient taking into account the glial cells and take less space than nonmyelinated neurons if we talk about similar conduction velocities. I'll have to check this one just to be sure.
The human brain especially has a lot of glia (90% of brain tissue) whereas for a mouse it's only 65% of brain tissue.
You mean the volume or the number of cells? This is certainly interesting and supports my hypothesis of why rodent neurons grow in size as their brains grow. What do you think?
Why are some brains less myelinated than others? Was their evolution just less lucky?
Possibly, but I'd caution against simplistic evolutionary arguments; evolution is rarely so simple. For instance, chimpanzees have higher axon myelination during development and adulthood than human brains do.
Notes I took while listening to the speech:
Eliezer Yudkowsky on Friendly AI
If the human race is down to 1000 people, what are the odds that it will continue and do well? I realize this is a nitpick-- the argument would be the same if the human race were reduced to a million or ten million.
Suppose that a blind person in a first world country wants help paying for a guide dog and/or wants guide dogs for other blind people in first world countries, but has heard of effective altruism. What honest arguments could the blind person use?
If I were designing an intelligence, I'm not sure how much control I would give it over its own brain. People are already able to damage themselves pretty badly, even with the crude tools they've got. I would experiment with intelligent species to see how they'd behave with more control over their brains. What would you do?
Sidenote: Birds show some possibilities of making brains more efficient per weight.
TED talk about neurons and brains. This is not a great TED talk, but it's got somewhat about comparisons between brains in different species, in particular that neuron size and density varies between species. Comparisons of brain size tells you less than people assume.
Brains and competition aren't just about sexual selection: Females (especially) compete for resources to feed and care for themselves and their children. In some species, males also compete for resources for their children. Reproductive selection isn't just about mating selection. See Mother Nature by Sarah Hrdy. Interview about humans as cooperative breeders
Do we need to think about hardware, software, and firmware (at least) for brains, rather than just hardware and software?
[Sound cuts off at 38:00. comes back at 39:10]
How much of organisms consist of traits which aren't being selected for?
The sound quality deteriorates enough at about an hour that I'm giving up.