Questions about genders ... male/female

[Reader]

Reader, this represents the most common misunderstanding of evolution that comes from theists. (Not saying you are a theist, just saying that they bring this up too often.)

Evolution does not necessitate that everything trend towards infinity. What I mean by this is that if an organism is perfectly suited to it's environment, then we wouldn't expect any genetic drift. Obviously no organism is perfectly suited to its environment, so there is always space to improve in some areas. However, if a certain aspect of anatomy or physiology functions very well, then there is very little selection pressure. So even if a new gender were to have mutated, it would have very likely been ousted very quickly, as the likelihood that a single new gender would be able to reproduce would be pretty low. In fact, two new genders would likely have had to mutate pretty early in the evolutionary process at the same time within the same population in order for them to have been sexually selected.

Two genders is all that is needed. And if things had gone differently very early on, I might be saying "six genders is all that is needed."

Thank you! Yes, this is the answer I was looking for! Thanks for clarifying it in layman's terms. A couple of more questions if you don't mind ... I asked this above in another post, but will ask here again a different way. So, if we started off as one "sex" ... how did we get to two sexes? How many of the one "sex" did we have until we evolved into another to be able to reproduce? Would the first "sex" have died off before more could be "made"? Does that makes sense? Trying to think this through before we talk about it in class.

[Jackalope]

Reader, this represents the most common misunderstanding of evolution that comes from theists. (Not saying you are a theist, just saying that they bring this up too often.)

Evolution does not necessitate that everything trend towards infinity. What I mean by this is that if an organism is perfectly suited to it's environment, then we wouldn't expect any genetic drift. Obviously no organism is perfectly suited to its environment, so there is always space to improve in some areas. However, if a certain aspect of anatomy or physiology functions very well, then there is very little selection pressure. So even if a new gender were to have mutated, it would have very likely been ousted very quickly, as the likelihood that a single new gender would be able to reproduce would be pretty low. In fact, two new genders would likely have had to mutate pretty early in the evolutionary process at the same time within the same population in order for them to have been sexually selected.

Two genders is all that is needed. And if things had gone differently very early on, I might be saying "six genders is all that is needed."

Thank you! Yes, this is the answer I was looking for! Thanks for clarifying it in layman's terms. A couple of more questions if you don't mind ... I asked this above in another post, but will ask here again a different way. So, if we started off as one "sex" ... how did we get to two sexes? How many of the one "sex" did we have until we evolved into another to be able to reproduce? Would the first "sex" have died off before more could be "made"? Does that makes sense? Trying to think this through before we talk about it in class.

If you're referring to humans, humans have always reproduced sexually, as have our ancestral species, until you go very, very far back. That species would not resemble humanity.

[Aractus]

Greetings!

I'm new here, so I'll add a short reason why I am asking this question on this forum.

I teach worldviews classes to high schoolers. We cover Secularism, Postmodernism, Islam, New Spirituality, Christianity and Marxism. Within each worldview we cover each discipline of theology, philosophy, history, economics, sociology, ethics, biology, psychology, law and politics and how they differ across the board.

We are currently in the biology unit ... and I've pondered this question from an atheistic evolutionary viewpoint for a bit ... and I can't seem to find an answer.

So, I thought I would post here to see if you all could offer some insight.

Why do we only have two genders, male and female? [excluding asexual animal reproduction] ... just humans and almost all animals? Why only two? Why not ... say ... seven, or seven-thousand? If we have evolved over time from a single celled organism ... why did we only evolve into two genders and not more? Why did it stop at two? Thanks for your time.

That's an excellent question, and also to the forums.

The reason for two is genetic mixing - i.e. you get 50% of your genes from your father and 50% from your mother. There's no need for more than two genders because each generation mixes those genes more and more (by not exclusively practising incest).

The other reason I can think of is DNA itself - it's made up of pairs of chromosomes, in our case (as humans) we have 23 pairs. The sex chromosome is what determines gender - so two X chromosomes produces female and an XY produces male, in humans anyway. In birds it's the opposite - ZW is female and ZZ is male.

Anyway, because we have pairs of chromosomes one of each pair comes from each parent (and is uniquely made up from their original two pairs, except for the paternal sex chromosome which is passed on unchanged). You can't really have more than two genders give an equal participation in the genes, but two genders works perfectly with the system for the parents to each have equal 50-50 participation of the genes of the offspring.

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You're forgetting transgenders, my friend. The issue isn't as clear cut as it seems.

That doesn't apply to biology.

[SteelCurtain]

Thank you! Yes, this is the answer I was looking for! Thanks for clarifying it in layman's terms. A couple of more questions if you don't mind ... I asked this above in another post, but will ask here again a different way. So, if we started off as one "sex" ... how did we get to two sexes? How many of the one "sex" did we have until we evolved another to be able to reproduce? Would the first "sex" have died off before more could be "made"? Does that makes sense? Trying to think this through before we talk about it in class.

The idea is that genders didn't evolve, sex itself did. So before sexual reproduction, there were no "male" or "female." Genders were a product of sexual reproduction evolving. Male and female are just the two carriers of genetic information. The advantage is that with the genetic information coming from two different places, there is a greater variation, and therefore a greater possibility of passing on advantageous information.

My guess is that there is a sweet spot. If reproduction required three parents instead of two, the advantage in extra genetic information might be outweighed by the difficulty in gaining a third partner.

[popeyespappy]

Evolution does not necessitate that everything trend towards infinity. What I mean by this is that if an organism is perfectly suited to it's environment, then we wouldn't expect any genetic drift. Obviously no organism is perfectly suited to its environment, so there is always space to improve in some areas. However, if a certain aspect of anatomy or physiology functions very well, then there is very little selection pressure.

Genetic drift within a population doesn't stop no matter how perfectly suited to an environment an organism might be. The DNA of each new generation is going to be different than that of their ancestors. Removing natural selection from the equation by reducing environmental pressure does not stop the gene pool from changing over time. Genetic drift does however tend to reduce variation within the population over time which is a bad thing should there be an environmental change because selection only works if there is variation.

[SteelCurtain]

You're absolutely right. I shouldn't have used that term. I guess I meant that the amount of deleterious mutations for an organism that is hypothetically perfectly suited to it's environment would be 100%.

Apologies, and I stand corrected.

[Esquilax]

Thanks, Beccs! I call it atheistic, because God is taken out of the equation. But the question is ... why did we stop evolving after two genders? Why don't we have more now? Like 7 or 7,000 or something along those lines?

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Something else that needs to be pointed out is that we didn't stop evolving at any point. In fact, we are in a continuous state of evolution, generation by generation, in small but significant ways. So when you ask why we stopped evolving genders after the second one, my answer would be... we haven't. Who knows what the future will bring? There's nothing specifically preventing another gender from emerging, although given our historical reactions to new things regarding sexuality one could argue that such a thing would be a detriment to survival. It could very well be that a newly emerged gender could be "fixed" to fit within the current paradigm with surgery or oppression or any number of cultural influences... if we recall how powerful the pressure was for gays to stay in the closet just a few decades ago, if there was a newly minted gender... how would you know?

Because just speaking in terms of probability, the chances of the first of that kind arising in a place that's progressive enough not to do anything about it is pretty slim, assuming this new gender is even recognized as a valid organic structure and not a deformity by a medical community trained to deal with a two gender binary. This rabbit hole goes deep.

[rexbeccarox]

First, usually "sex" refers to biological characteristics, and "gender" refers to social and cultural characterizations; usually self-characterizations.

Second, there are many different genders. Also, there are at least three different sexes: female, male, and intersex.

Third, what would more sexes even look like? We have everything we need to procreate; why would we evolve anything more, less, or different?

[Whateverist]

If we have evolved over time from a single celled organism ... why did we only evolve into two genders and not more? Why did it stop at two? Thanks for your time.

I'd say sex comes at a cost. It is less assured and reliable, but then it kicks evolution into high gear. We wouldn't be asking the question without it. But what really would more genders add? Presumably the costs would go up but it is hard to see where the benefit to evolution would come from. Perhaps two sexes is the minimum price to pay for accelerated evolution.

You can add death on the cost side of the ledger.

[Aractus]

Second, there are many different genders. Also, there are at least three different sexes: female, male, and intersex.

No there aren't, at least not in the eyes of biology. Inter-sex people are still either biologically male if they have a Y chromosome, and female if they don't. Example: people who have androgen-insensitivity syndrome AND have XY chromosomes are still biologically male even though their genitalia resembles female anatomy, and they will grow breasts at puberty. They do not have a womb, or a vagina, and have testicles and not ovaries. Here's an example:

Nudity below, these three siblings are genetically males and have androgen-insensitivity syndrome:

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This picture is from a textbook, it can be found on p. 1036 of "Anatomy & Physiology 6th ed" by K. Saladin 2012.

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