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I guess this is big brain week.

The latest episode of the Brain Science Podcast has an interview with Gary Lynch discussing his book Big Brain: The Origins and Future of Human Intelligence.

A very accessible discussion of, among other things, how the human brain evolved to be so big. His position is that there was no natural selection pressure in favor of greater intelligence (even today, many, many people do just fine with very limited intelligence. Just look at Sarah Palin!).

Rather, when our distant ancestors became bipedal, the size of the birth canal increased, and this led to larger-brained babies.

Intelligence was just an accidental side effect.

This is actually something that I had wondered about.

Since the human birth canal puts a limit on the size of babies' heads, could the availability of Cesarean sections cause humans to evolve to have larger brains?

Turns out the answer might be yes:

Babies have very big heads that squeeze with only great difficulty through a relatively narrow pelvis, so the relationship in size between head diameter and the diameter of the pelvic opening has been a limitation on human evolution. We know this had to be a factor in our evolution: the average newborn mammal has a cranial capacity that is roughly 50% of the adult size, chimpanzee babies have heads about 40% of the adult size, but human babies have crania that are only 23% of what they will be in adults. While our brains have gotten larger over evolutionary time, they have not gotten proportionally larger in utero, because large-headed babies increase the difficulty of labor and cause increased mortality in childbirth. If childbirth could bypass the pelvic bottleneck, that would allow for fetal heads to grow larger without increasing the risk of killing mother and/or child.

Read the rest of PZ Myers's post on Will the availability of C-sections give humans bigger brains?

Mark Liberman discusses how hard it is to count a language's active vocabulary:

Consider the counting problem with respect to the text of your question. Your note uses the strings language, languages, language's. The word-count tool in MS Word will (sensibly enough) count each of these as one "word". But how many different vocabulary items -- word types -- are they? Are these three items, just as written? Or should we count the noun language plus the plural marker -s and the possessive 's? Or should we just count one item language, which happens to occur in three forms?

Your question also includes the strings am, are, be, is, was -- are these five distinct vocabulary items, or five forms of the one verb be? How about the strings weeks, weekly, day, daily? Is weekly the same vocabulary item as an adjective ("on a weekly basis") and an adverb ("published weekly")? If we analyze weekly as week + -ly and significantly as significant + -ly, are those (sometimes or always) the same -ly?

What about the noun use (in "daily use") and the participle used ("used on a daily basis"). Are those different words, or different forms of the same word? Is the participle used the same item, as a whole or in parts, as the preterite used?

Should we unpack 90% as "ninety percent" (two words) or "ninety per cent" (three words)? And is percentage a completely different vocabulary item, or is it percent (or per + cent) + -age?

Depending on the answers to these five easy questions about 17 character strings, we might count as many as 18 vocabulary items or as few as 10. And as we scan more text, this spread will grow, without any obvious bounds.

The whole article is worth a look.