Speciation: If you don't sleep together, you soon won't cheep together?

Speciation, we are told, is "notoriously hard" to observe in action - a remarkable fact, given that it is so common, according to most sources.

Sometimes, researchers are driven to rely on for very slight evidence indeed.

"The question of whether these two populations are on the road to speciation comes down to sex. When two populations stop exchanging genes—that is, stop mating with each other—then they can be considered distinct species. Uy and his team wanted to see if these flycatchers were heading in that direction."

Well, they might head in that direction, or they might head back again if a shortage of, say, lady birds in one group threatens to disrupt the mating season.

Anyway, pardon me, but isn’t "When two populations stop exchanging genes—that is, stop mating with each other—then they can be considered distinct species." like saying that a couple can be considered no longer married if they are no longer sharing a bedroom?

How do we know that won’t change? Prudent people wouldn’t consider them “no longer married” unless they moved to separate addresses and file for divorce.

Doesn’t this story really show how rare evidence of speciation is?

I mean, if scientists are relying on this kind of thing, it’s the same principle as:

In the quiet Canadian community of Wawa Waupoos, where nothing much ever happens (if you don’t count occasional drunken driving and ice fishing deaths), neighbours try to find out surreptitiously if couples still sleep in the same room. Lord knows, that’s all that those neighbourly investigators have to go on - and in the winter, it is all they have got to do as well, unless you count daytime TV.

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