Hacker News Reader

Comment by tsimionescu | Hacker News Reader

Note that many, many animals have non-genetic sex determination. Most fish, amphibians, and reptiles have the same genes for both males and females. Sexual differentiation typically depends on things like the egg temperature or salinity and so on. Some species can even change sex during their adult lifetimes, with external conditions triggering a complex hormonal shift that convert an adult, fertile male into an adult, fertile female.

Having genetic differences between males and females is mostly a bird and mammal thing, at least among vertebrates.

View on HN

> Having genetic differences between males and females is mostly a bird and mammal thing, at least among vertebrates.

Also: the configuration and function of sex chromosomes is not consistent even within mammals. There are a number of species - primarily rodents - with unusual sex-determining systems, like species with XX/X0 (i.e. where males have an unpaired X chromosome) or even X0/X0.

https://pmc.ncbi.nlm.nih.gov/articles/PMC8617835/

Important plot element in Jurassic Park!

Man, the bible missed all of this when they were talking about the two animals of every species on the Ark. What else did they leave out?

To be fair, you almost always still need two individuals to get reproduction going - you just don't need to be as picky about which two individuals as you might think. There are a rare few animals that can sometimes self-reproduce, but it's not a common strategy in the animal kingdom, even among hermaphroditic animals.

Parthenogenesis is not uncommon in animals: https://en.wikipedia.org/wiki/List_of_taxa_that_use_partheno... (I am mostly quibbling with "rare few animals" but I can't really say much about the relative prevalence of parthenogenesis compared to sexual reproduction.

They're less rare than you might think. Parthenogenesis ("virgin birth") occasionally occurs in some domestic birds, including chickens and turkeys. Due to the way sex determination works in birds, the offspring created this way are always male.

https://www.sciencedirect.com/science/article/pii/S003257911...

There are also a number of species of lizards, and one snake, which reproduce exclusively via parthenogenesis: https://en.wikipedia.org/wiki/Parthenogenesis_in_squamates

In some though not all such species, there are no known male examples _at all_ (though in reptiles some forms of parthenogenesis can produce males).

Thank you so much for introducing me to this concept. I knew the word thanks to Shriekback. I used to have ducks. At one point when I only had 3 females, I found a broken egg with a fetus in it. I knew they were all female, but couldn't convince anybody of what I saw.

They were actually intelligently designed this way any animal you can’t sex easily as a hermaphrodite

Here's some punctuation: ....,,,;;;:::!!!???

I don't have the space to help on your other issues.

That's ok, the space key seems to work just fine :troll:

This always struck me as a bit odd, because it was a somewhat common belief around then, and for long after, that many animals reproduced by abiogenesis anyway. Why bother taking two mice on the ark; everyone knows that mice spontaneously emerge from river mud!

(It’s possible that this was just a Greek quirk and never made it to Palestine, I suppose.)

The idea persisted into the Middle Ages. Can't say for certain that it was continuous, however; the medieval supporters quoted Aristotle et al.

Listen, we still don't know how eels reproduce. Our knowledge has never been all inclusive and properly disseminated. The fearful cave-dwelling scribes who wrote the old testament were clearly not up to date on their biology.

I didn't know either, but hn came to the rescue. In case you're one of today's lucky 10000:

https://www.newyorker.com/magazine/2020/05/25/where-do-eels-...

I think eels are safely outside the domain of knowledge where anyone could safely say "everybody knows that!"

https://xkcd.com/2501/

Well, no, I’m actually surprised that whoever wrote the Old Testament _was_ up enough on their biology (or at least aligned with biology, however accidentally) to realise that most animals reproduce sexually. This certainly wasn’t the conventional view in the Greek world, say, nor was it in the West until the 18th century or so.

What was this view exactly? They would have know their pets and farm animals reproduced sexually. I guess it isn't a leap to think all mammals? So what animals did they think did not?

Mice, flies, vermin of various kinds that seemed able to show up anywhere from no obvious parents.

So, we tend to think that it’s just common sense that most animals reproduce sexually (actually I think most people would assume that _all_ animals do; in fact, as with most things, there are edge cases), but, well, to an extent that’s because we already know that. The historical view was a bit different: https://en.wikipedia.org/wiki/Spontaneous_generation

This isn’t even the only weird idea that people used to have about reproduction; there’s also stuff like https://en.wikipedia.org/wiki/Barnacle_goose_myth

We do now!! It’s fascinating. Look it up!

> What else did they leave out?

Plants. Fungi.

The latter they brought with an especially rank pot of Grandma Noah's sauerkraut.

Leviticus rightfully instructs you not to eat bats, but it seems to mistake them for special birds rather than mammals.

There can't be much meat on a bat anyway.

there's not much on a snail either, but they're still delicious.

They're fine. Mostly the butter stuff tastes good. I wouldn't put snail up there with badger or owl.

Wait, is there a _specific_ prohibition? Like, they fail Old Testament dietary rules miserably _anyway_.

These are the birds you are to regard as unclean and not eat because they are unclean: the eagle, the vulture, [a bunch of other birds] and the bat"

https://www.biblegateway.com/passage/?search=Leviticus%2011:...

Aaah, right, I suppose if you’re assuming it’s a bird it _would_ need a specific call-out, yeah. I was assuming it’d be covered by the hooves-and-stomachs stuff, but if you don’t think it’s a mammal in the first place that wouldn’t work.

(From the above: “Bible Gateway is currently unavailable to consumers in the United Kingdom and European Union due to technical issues.” I am now very curious just which EU regulation the bible website was worried about.)

It was an early deployment of RAID1. Two copies of everything

Reply on news.ycombinator.com