41.   I have a running conversation with a friend about the problem of whether humans have free will.

42.   Humans also have place cells, Wilson said.

43.   Humans generally have two lobes in the left lung, three in the right lung.

44.   Humans have always had a deep wish to learn more about nature by experiment.

45.   Humans have less hair than our ape and monkey cousins, and we walk on two feet.

46.   Humans have only a moderate amount of REM sleep, Siegel said, and dolphins, generally considered to be intelligent mammals, have very little REM sleep.

47.   Humans have powerful sweat glands, and because they are virtually hairless, the sweat works to cool down the skin through evaporative cooling.

48.   Humans have some of these protections as well, but species that rely on scavenging might well be better equipped to handle noxious foods.

49.   If these efficient woodpeckers preparing their nursery can stay on track, then why do higher-order humans have so much trouble?

50.   If humans have a similar system, then drugs that block the receptor could prevent hair loss.