Who appeared first - males or females?
- Thread starter Olga
- Start date
TheVat
Valued Senior Member
Anyway, she let me know it was a fluke, so all good now. I still think a VPN would fix this whole translation issue since she could then just access Google without the Russian throttling and get her posts translated.
Неа, он с ним вообще не работает.
Wizard of Whatever
Registered Senior Member
Even when commensurable, allegory is for literary intellectuals, not science research that entails precise nomenclature or non-ambiguous description. Albeit, the shop-talk can be Greek to those outside a discipline, and the publishing standards of today probably allow spasms of fashionable, inscrutable vagueness.
But science communicators -- mediating between experts and the public -- doubtless engage in figurative depictions and analogies at times. So there's a nook.
_
Olga:
"Male" and "female" in biology refer back to the gametes produced by sexually-reproducing species. Typically, there are larger and smaller gametes. The individuals of the species with the larger gametes are conventionally referred to as "female", while the individuals with the smaller gametes are referred to as "male".
In the plant world, as I understand it, things are a bit complicated. A single plant can produce both large and small gametes. Therefore, it doesn't make a lot of sense to say that the plant is either female or male.
A lot of species reproduce asexually. Some species undergo transitions from producing large gametes to small ones or vice versa during their life cycles.
Human beings are descended from earlier apes, which are mammals. Amongst the mammals, typically individual animals produce either large gametes or small ones, exclusively.
It doesn't make much sense to ask "which appeared first - males or females?" In sexually-reproducing species, males and females came into existence simultaneously.
Think about this, for instance: suppose there was some species that only had females, but the females were unable to reproduce without receiving male gametes from another member of the species. What would happen, in that case? Clearly, the females would all fail to reproduce and the species would die out. The same argument applies to a theoretical males-only species that required sexual reproduction.
Clearly, the only way for sexually-reproducing species to exist is if females and males developed simultaneously.
You might also ask the question: why are there only two sexes, and not three or seven? I would guess that's due to natural selection. Suppose a species evolved that had three sexes, such that all acts of reproduction required three individuals to come together to mix the three types of gametes. That would be less likely to occur than species with two types of gametes to reproduce. Therefore, it would lead to a situation where the two-sex species vastly overproduced offspring, in comparison to the three-sex species. The most likely outcome is that any three-sex species would go extinct.
"Male" and "female" in biology refer back to the gametes produced by sexually-reproducing species. Typically, there are larger and smaller gametes. The individuals of the species with the larger gametes are conventionally referred to as "female", while the individuals with the smaller gametes are referred to as "male".
In the plant world, as I understand it, things are a bit complicated. A single plant can produce both large and small gametes. Therefore, it doesn't make a lot of sense to say that the plant is either female or male.
A lot of species reproduce asexually. Some species undergo transitions from producing large gametes to small ones or vice versa during their life cycles.
Human beings are descended from earlier apes, which are mammals. Amongst the mammals, typically individual animals produce either large gametes or small ones, exclusively.
It doesn't make much sense to ask "which appeared first - males or females?" In sexually-reproducing species, males and females came into existence simultaneously.
Think about this, for instance: suppose there was some species that only had females, but the females were unable to reproduce without receiving male gametes from another member of the species. What would happen, in that case? Clearly, the females would all fail to reproduce and the species would die out. The same argument applies to a theoretical males-only species that required sexual reproduction.
Clearly, the only way for sexually-reproducing species to exist is if females and males developed simultaneously.
You might also ask the question: why are there only two sexes, and not three or seven? I would guess that's due to natural selection. Suppose a species evolved that had three sexes, such that all acts of reproduction required three individuals to come together to mix the three types of gametes. That would be less likely to occur than species with two types of gametes to reproduce. Therefore, it would lead to a situation where the two-sex species vastly overproduced offspring, in comparison to the three-sex species. The most likely outcome is that any three-sex species would go extinct.
А если бы гипотетически все являлись гермофродитами? Они могли бы сами себя оплодотворять? А потом от них отделилась какая-нибудь неполноценная особь, ставшая женской?
Yes. However, in reality most simultaneous hermaphrodites prefer to mate with a different individual. Again, there is an evolutionary driver there. A hermaphrodite that self-fertilises its ova essentially produces offspring that are clones of the original individual. This does not increase genetic diversity, which leaves the offspring vulnerable to all the genetic defects and vulnerabilities the original individual had.
Neverthless, if for some reason the availability of other individuals to mate with is scarce, hermaphrodites do sometimes self-fertilise.
Some species are sequential hermaphrodites (e.g. clownfish). They change sex at some point during their lifecycle. But they cannot self-fertilise.
I don't know what you mean by "inferior" in this context.
However, hermaphroditism almost certainly evolved earlier than the separation into distinct males and females. The best-supported evolutionary models show that early sexual eukaryotes were functionally hermaphroditic, and that separate sexes (gonochorism) arose later through specialisation.
The earliest eukaryotes capable of sexual reproduction were single-celled organisms that did not have distinct male/female roles; essentially, these were single organisms performed both gamete roles.
Gradually, gametes evolved into large nutrient-rich ova and smaller, mobile sperm.
Once gametes diverged into two types (small vs. large), evolutionary pressures favored individuals specializing in one role or the other. This specialization increased reproductive efficiency, reduced conflict between male and female functions and allowed for more complex mating strategies.
The Y chromosome is effectively a truncated X chromosome. That's vastly oversimplified, since the Y chromosome is less than 3/4 of the X chromosome, and can no longer recombine with X chromosomes during meiosis. But originally there was a lot of overlap.
Pinball1970
Valued Senior Member
I don't think there is one solid theory on this. From what I have looked at, sexual reproduction arose via DNA repair mechanisms but I am not clear on the details.
Пин, а если поместить двух детей на необитаемый остров, чтобы они ничего не знали о том, как происходит размножение - они вообще смогут размножиться когда вырастут? У животных понятно - у них инстинкты, но у людей считается, что инстинктов нет никаких, кроме инстинкта боязни змей. Тогда как они поймут, что им нужно делать?
Pinball1970
Valued Senior Member
You have just described, "The Blue lagoon" 1980, a truly awful film with Brook Shields.
Two kids shipwrecked who grow together eventually finding love/sex.
Ну это в фильме, а в реальности что могло бы быть?
Pinball1970
Valued Senior Member
Same. We are animals and they would end up doing what animals do.
Пин, а как они узнают, что нужно делать определённые действия, если они нигде этого не видели ранее?
It depends. Are the child both male? Both female? Or one male and one female?
Ну, у нас в России ещё не научились размножаться почкованием. Так что, вероятно, это должны быть мальчик и девочка.It depends. Are the child both male? Both female? Or one male and one female?
Pinball1970
Valued Senior Member
Sex, sexualy is innate in us. If you put them on a kids, by the time they hit puberty they will be experimenting and will have sex. Possibly before puberty.
Тогда почему считается, что у людей нет инстинкта размножения? Разве сексуальность - это не инстинкт?