They’re big, they’re creepy and they grab their prey with terrifying speed. And female Komodo dragons have one other talent: without having sex, they can lay eggs that develop into healthy male offspring. Scientists realized this only in 2006, after a female dragon named Flora, which lived in a zoo and had never been exposed to male dragons, laid a clutch of eggs that hatched normally.
In Komodos, the process seems to start with eggs that are like any other, with half the number of required chromosomes. But at some point in the development process, the chromosome count doubles back up and a Komodo embryo results. Only males can result from this process. That’s because in Komodo dragons, females are the ones that have two different sex chromosomes—in this case a Z and a W. Males are ZZ. When the chromosomes in an egg divide and then multiply themselves by two, they can thus produce only a non-viable WW or a viable ZZ—a male. The implication—and perhaps the very reason for this arrangement—is that it would allow a female Komodo to swim to an isolated island and produce her own sexually reproducing population, using her sons as mates once they reached maturity. Nobody said nature was always pretty.
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