Two interesting items on human evolution

Next time you're walking in the woods, give a thought to our early arboreal ancestors leaping from tree to tree...

By scanning a 54-million-year-old skull roughly the size of a walnut, scientists have created the first virtual 3-D model of an early primate brain, a new study says. Surprisingly, the model suggests that primates (such as lemurs, monkeys, apes, and humans, among others) might have evolved larger brains as a result of the need to move quickly from tree to tree—not, as commonly assumed, to hunt for fruit or navigate within a single tree. ---http://tinyurl.com/nvnjsz

... trying desperately to escape from constricting snakes:

The ability to detect threatening snakes may have shaped the visual system of our primate ancestors, a new study says.

In a sort of evolutionary arms race, primates kept improving their eyesight to help spot and avoid snakes as the snakes became more dangerous, suggests Lynne Isbell, a behavioral ecologist at the University of California, Davis.

"The initial change in primate [eyes] ... occurred when they had to deal with constricting snakes, probably about 90 million years ago," Isbell said. --- http://tinyurl.com/n4cqlb

Note that the latter item dates to a time in evolutionary history almost twice as far back as the former. This may suggest why ophidiophobia --- the fear of snakes --- may be such a deeply-rooted instinct!