Sharks have been around a lot longer than humans. Do you think they will outlast us?

Lisa Ennis
Westchester, PA

The earliest cartilaginous fishes, descendants of the sharks and rays, were present 375 million years ago. This is long before the arrival of modern man less than a million years ago. The sharks have lasted due to their sensory abilities—keen hearing, smell, and electric sensibility—large protruding mouth, and swimming ability. Humans, on the other hand, do not have as well-developed senses and a smaller mouth, but have evolved a larger brain and a variety to their behavior that has enabled them to succeed in the modern environment. One cannot say at this point which will outlast the other, humans or sharks, though sharks suffer more from human fishing than humans do from the rare shark attack.

How much is known about sharks' family life? For example, do mothers teach baby sharks how to hunt before letting them loose in the wilds?

(name witheld by request)

Most species of sharks give birth to perfectly formed young that can search for prey as soon as they're born. Sharks locate their prey by the low-frequency sounds emitted during swimming and other activities. In one case, sounds that attracted adult sharks to a speaker were played back to baby sharks just after birth. These sharks were attracted to the sounds without having any prior experience, indicating that this crucial ability is stored within the animal's genetic code.

It is possible that sharks remain together in family groups after birth. Fishermen rarely catch white sharks, but when they do the fishermen capture more than one individual, indicating that they may school together. Several small white sharks were recently filmed swimming together off Southern California. The question of whether they come from the same mother could be answered by collecting tiny samples of the shark's body and looking for a similarity in their genetic codes.