animals, the reptiles, developed a self-
contained egg with a leathery skin that slowed
fatal water loss, and with enough food to
support prolonged embryonic development
into a fully formed animal. The eggs of birds,
animals that arose some 100 million years
later, are a refined version of the primitive
reptile egg. Their hard, mineralized shell is
impermeable enough that the embryo can
develop in the driest habitats; and they
contain an array of antimicrobial defenses.
These developments made the bird egg into an
ideal human food. It contains a sizeable and
balanced portion of animal nutrients; and it’s
so well packaged that it keeps for weeks with
little or no care.
The Chicken, from Jungle
to Barnyard
Eggs, then, are nearly a billion years older
than the oldest birds. The genus Gallus, to