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Comment by feketegy | Hacker News Reader

It's not that black or white though, more than 60% of the World population has been infected with Toxoplasmosis, yet you don't see people running towards lions at every corner.

The path how the parasite infects rodents, then cats, then humans is very complex and not at all consistent, most articles on the Internet dumb it down way too much.

This Youtuber has an awesome explanation on it: https://www.youtube.com/watch?v=rdlHNhrMw-A

Also, his channel is translated from Hungarian, it's an awesome channel btw.

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> yet you don't see people running towards lions at every corner

Oh, but you do see people running towards cats! They keep them indoors and feed them.

The article described something specific that could be tested. I leave it to the scientist to design a similarly specific experiment for humans. Also the "reckless" behaviour exhibited by the cubs disappeared after there were older than 1 year:

While uninfected cubs stayed an average of 300 feet away from lions, cubs that had Toxoplasma antibodies in their blood had ventured within an average of 142 feet from the predators, a dangerous proximity. These differences disappeared after the cubs turned one, perhaps because the survivors learned not to get too close to the felines.

so those infected survivors got much closer than the healthy ones and yet survived. Sounds like a [harsh] filter for the high survivability traits which may be beneficial for the population, and that may explain why the [susceptibility to the] infection hasn't been selected out.

Possibly, but luck isn’t an inheritable trait.

It is in humans.

... according to Larry Niven.

And Rockefeller, Cargil, Rothschild ...

What makes you think there was inherited luck involved?

People make their own 'luck'.

Luck and Inherited Luck are different things.

Yes.

> [...] which may be beneficial for the population, [...]

Do keep in mind that evolution mostly works on the level of genes, and perhaps individuals. It doesn't really work on the level of the population.

See eg https://en.wikipedia.org/wiki/Group_selection

> yet you don't see people running towards lions at every corner.

The headline says more reckless.

I wouldn’t consider it a stretch to say some people are definitely more reckless. Whether there’s a causal link, I couldn’t say.

There's a theory that toxoplasmosis, given it can transfer from cats to humans, is the reason for the 'crazy cat lady' stereotype. Certainly, cat owners I've known seem more likely to have 'attacks' of extreme aggression than the general population, and giving vent to that does seem like a 'risk' to our status in the community that most of us don't take. Then again, having that sort of temperament may make someone more suited to owning cats than other pets...

Perhaps in more complex organisms there is a more complex response to the pathogen? It could trigger any number of maladaptive behaviors in humans and it would be hard to know if it was the parasite or one of the many other unfortunate environmental factors of the modern world.

It might even trigger adaptive behaviours.

Toxoplasma is dormant in humans.

What is really interesting – how human toxoplasma prevalence varies per country.

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