372 Evolution? The Fossils Say YES!
(A) (B)
FIGURE 15.10. (A) Juvenile chimpanzees have many characteristics of the skull found in adult humans, including
upright posture, relatively large brain, small brow ridges, and a less protruding snout. (B) As they grow into
adult chimps, these features all become more apelike. Since the 1920s, many anthropologists have argued
that much of what makes us human is retention of juvenile ape characteristics into adulthood (neoteny). (From
Naef 1926)
In fact, since the 1920s, many biologists and anthropologists have argued that much
of what differentiates us from the chimpanzee is neotenic retentions of juvenile ape char-
acters. If you look at a juvenile chimpanzee (fig. 15.10), its skull is much like that of a
human, with a large brain, small brow ridges, short snout, and upright posture. Then, dur-
ing development to an adult, the chimpanzee develops the larger snout with long canines,
big brow ridges, and forward slouching posture of the head. If regulatory genes tweak our
embryonic development a tiny bit, we can make most of the characteristics that mark us
as human just by becoming juvenile apes that reach sexual maturity without every truly
growing up.
You may have read some of the fascinating works of Aldous Huxley, the famous novel-
ist and author of the dystopian classic Brave New World (a high school reading list favorite).
He was also the brother of the famous evolutionary biologist Julian Huxley, and both were
grandsons of Darwin’s “bulldog,” Thomas Henry Huxley. Aldous knew these ideas about
human neoteny very well because of his brother’s influence. In 1939, he published a novel
entitled After Many a Summer Dies the Swan. The theme of the novel is immortality, and
how humans are always striving to find a way to extend their lives beyond what nature
intended. The main character is a millionaire (modeled after William Randolph Hearst,
whom Huxley met when he was a Hollywood screenwriter in the 1920s) named Jo Stoyte,
who is attempting to live forever by hiring a classic “mad scientist,” Dr. Obispo, to do