How does Head lice start?

Question

I understand that you get lice from person to person contact.Eventually there was a beginning, a patient zero, a start. Not just generational growth

In: Biology

Answer 1

>Eventually there was a beginning, a patient zero, a start

The earliest fossil we have of an insect that is recognizably a louse is from roughly 100 million years ago. Their anatomy suggests that they were already parasites; scientists found some of them on fossilized feathers, suggesting that they were parasitizing feathered dinosaurs.

We have also found louse-like fossils from roughly 150 million years ago which seem to have partially-parasitical anatomy. Thought it’s possible that there were already fully parasitic lice then: after all, parasitic and nonparasitic lice both exist today. Apparently completely non-parasitic lice have been found as far back as ~300 million years.

So, probably some time between 150 and 100 million years ago, lice became parasitic. They hung out on feathered dinosaurs, using the feathers to keep warm like they use modern hair (and earlier clothes lice used clothes).

How exactly animals become parasites is complicated but seems to happen quickly; it’s especially interesting because the “ancestral lice” we’ve found don’t even seem to be predators.

The earliest fossil we have that we think has fur is from ~250 million years ago. So probably at some point a furred proto-mammal was hanging out with a feathered dinosaur (or had some contact, perhaps by stealing eggs or chicks from a nest) and some lice figured out that mammals are fine to parasitize too.

Presumably various strains of lice evolved with some line of mammal over the eons, and when humans evolved, our little buddies had been with us every step of the way.

It’s possible that alternatively humans evolved from a louseless population and later got “infected” by lice from different mammals. Hell, we could even have been infected directly from birds! But scientists have tracked lice and compared human lice with chimpanzee lice and are pretty sure we’ve had lice since at least before we split from chimps.