Dawn of the Y: Papaya—Glimpse of early sex chromosome

The papaya plant carries the youngest Y chromosome ever found, reports a research team. That sex chromosome is so new evolutionarily that it doesn’t have the stripped-down style of full-fledged Y chromosomes.

INVENTING SEXES. Papaya plants can be male, female, or some of both, thanks to incipient sex chromosomes that may show how sex chromosomes arise.