What if humans were to have not otherwise evolved as male and female in separate bodies?

[JohnDBarrow]

Being natural hermaphrodites seems to work well for earthworms, but most other natural animal species NORMALLY have male and female in separate bodies.  Is having male and female in separate bodies a practical reproductive plan for humans, mammals, birds and etc?  In Man's various cultures, this separate male and female setup seems to have been the cause of a lot of social inequalities since man first picked up a stone and cast it.  One such sex inequality invented by Man has been "ladies first".  What are the pros and cons of having a species set up by nature as hermaphrodites as opposed to having a species divided with separate male and female individuals? 

 

What is the advantage to having human individuals divided by sex? 

In nature, male lions don't seem to understand the notion of 'ladies first' if you understand the pride's feeding order. 

[exchemist]

1 hour ago, JohnDBarrow said:

Being natural hermaphrodites seems to work well for earthworms, but most other natural animal species NORMALLY have male and female in separate bodies.  Is having male and female in separate bodies a practical reproductive plan for humans, mammals, birds and etc?  In Man's various cultures, this separate male and female setup seems to have been the cause of a lot of social inequalities since man first picked up a stone and cast it.  One such sex inequality invented by Man has been "ladies first".  What are the pros and cons of having a species set up by nature as hermaphrodites as opposed to having a species divided with separate male and female individuals? 

 

What is the advantage to having human individuals divided by sex? 

In nature, male lions don't seem to understand the notion of 'ladies first' if you understand the pride's feeding order. 

From what I read, the evolution of sexual reproduction is one of the unsolved problems in evolutionary biology. So a good question that is still awaiting a convincing answer.

[Bufofrog]

1 hour ago, JohnDBarrow said:

Is having male and female in separate bodies a practical reproductive plan for humans, mammals, birds and etc? 

I think the answer is a resounding yes.  Mammals have been around for 200 million years and birds have been around for 150 million years.  Sounds like it's working out just fine.

[swansont]

1 hour ago, JohnDBarrow said:

What is the advantage to having human individuals divided by sex? 

Genetic diversity. You’re getting genes from two different individuals each generation, or possibly each instance of mating.

[Sensei]

If you look at the biomass of organisms on Earth, you will see that most living organisms do not have sex at all or are hermaphrodites.

https://ourworldindata.org/life-on-earth

2 hours ago, JohnDBarrow said:

Is having male and female in separate bodies a practical reproductive plan for humans, mammals, birds and etc? 

Mammals evolved from reptiles, and these evolved from amphibians, and these evolved from fish. Something that works will not suddenly change into something else because it would disrupt the whole process of fetal development. Changes happen very slowly over millions of years.

[exchemist]

22 minutes ago, swansont said:

Genetic diversity. You’re getting genes from two different individuals each generation, or possibly each instance of mating.

But you also get that with hermaphrodites like garden snails.

[Sensei]

You might as well ask why a man has five fingers, or why he doesn't have six legs.

 

An interesting case is sequential hermaphroditism in fish that change gender:

https://en.wikipedia.org/wiki/Sequential_hermaphroditism

https://en.wikipedia.org/wiki/Moon_wrasse

Edited April 14 by Sensei

[swansont]

14 minutes ago, Sensei said:

If you look at the biomass of organisms on Earth, you will see that most living organisms do not have sex at all or are hermaphrodites.

Animals (specified in the OP) ≠ organisms

Plants can be male & female

8 minutes ago, exchemist said:

But you also get that with hermaphrodites like garden snails

Where does the other genetic material come from if the individual self-fertilizes?

If there are two, then you’re doing what sexual reproduction does, so it it’s an advantage, then it’s an advantage.

And AFAIK most hermaphroditic animals are invertebrates so there might be some limits on that mode of reproduction.

[Sensei]

11 minutes ago, swansont said:

And AFAIK most hermaphroditic animals are invertebrates so there might be some limits on that mode of reproduction.

Current animals and organisms are simply the lucky survivors of mass extinctions in the past.

[exchemist]

17 minutes ago, swansont said:

Animals (specified in the OP) ≠ organisms

Plants can be male & female

Where does the other genetic material come from if the individual self-fertilizes?

If there are two, then you’re doing what sexual reproduction does, so it it’s an advantage, then it’s an advantage.

And AFAIK most hermaphroditic animals are invertebrates so there might be some limits on that mode of reproduction.

What snails do is fertilise one another, I understand. 

[CharonY]

A few things should be added to lay the foundation for further discussions. First gonochorism (the term to describe a sexual system where there are male and female members) does not always have to be linked to sexual dimorphism (the term to describe differences in appearance between male and females of a species). Sexual dimorphism is often a consequence of the respective reproductive strategies. 

Among hermaphroditic species, one can actually also distinguish between various forms. The one OP is thinking about is considered simultaneous hermaphroditism, i.e. all individuals producing sperm and eggs, but there are also species who are sequential hermaphrodites. I.e. producing egg or sperm at different points in their life. 

Studies trying to figure out fitness benefits have been investigating closely related species in which all three strategies are found, e.g. in certain worms. Here, it was found that the different species had different reproductive characteristics, that likely have benefits under different conditions. Generally, they found a trade-off between fecundity (how much they reproduce) and survival. Simultaneous hermaphrodites had the highest survival rate, but least fecundity (and smallest eggs, indicative of lower maternal investment), whereas the opposite was found for sequential hermaphrodites. The gonochoristic species was somewhere in-between.  

Taking that all together (survival rate, reproduction over total life cycle etc.) it seemed that the dichoristic species had overall the highest fitness. They had higher fecundity in the early stages of life cycle. They outperform simultaneous hermaphrodites, which have lower fecundity. While sequential hermaphrodites are more fecund, they are delayed until their female phase, and during the whole life cycle they are not able to compensate the early advantage. Essentially they are able to reach sexual maturity faster, likely as they only need to produce one form of gametes. The disadvantage of that gonochoristic species pay is that they produce males, that cost the same as females (as eggs) but do not directly contribute to future generations (the limiting factors are the eggs). Hermaphroditism is speculated to be a primary advantage when population densities are low and it is difficult to find a mate. 

There are also evolutionary developmental consideration. Transition from hermaphrodite to gonochoristic species is comparatively easy, as it could be reasonably executed by suppressing the development of one sexual function. Conversely, there are more steps involved in transition from gonochorism to hermaphroditism. I.e. once gonochorism outcompetes hermaphroditism in the evolutionary history of species, it is very unlikely that they  hermaphroditism will develop, even if it became more advantageous.

[JohnDBarrow]

I dare say the hermaphroditic earthworms are quite populated worldwide. I understand it still takes two of these individuals to reproduce. Genetic diversity would still come from two separate individual earthworms which mate with one another. My theory is that if humans were also hermaphroditic and naturally able to continue their species, still two separate individuals would be in order to reproduce. A single individual entirely reproducing on its own in theory would indeed lack any genetic diversity. 

Here is a link (not safe for work) to a piece of artwork I made to provide you a mental picture of my notions of a hypothetical hermaphroditic human had Mother Nature otherwise gone that route or may still choose to go that route in the future before Man becomes entirely extinct should that be the fate for us. 

https://www.mediafire.com/view/94s6qklnc0xc3yx/concept_hermaphrodititc_human.png/file

 

My concept hermaphroditic human (the one that never happened but might still happen in the future) is conceived by me to possibly be able to both bear and sire healthy children under normal circumstances. The trouble is that uterine female mammals generally have limited physical strength and stamina. Since each and every of my theoretical hermaphroditic humans would have childbearing capability under normal circumstances, how well might they be able to do strenuous and dangerous labors? The non-childbearing men have a physical advantage over the childbearing women and therefore men have been assigned the more dangerous and difficult work for the longest time. Modern woke societal attitudes regarding sex and gender disregard such natural differences between men and women. But I digress. How might the hormones work in a single mammal's body with both impregnating and childbearing capabilities?  

 

 

Edited April 15 by JohnDBarrow

[dimreepr]

10 hours ago, JohnDBarrow said:

I dare say the hermaphroditic earthworms are quite populated worldwide. I understand it still takes two of these individuals to reproduce. Genetic diversity would still come from two separate individual earthworms which mate with one another. My theory is that if humans were also hermaphroditic and naturally able to continue their species, still two separate individuals would be in order to reproduce. A single individual entirely reproducing on its own in theory would indeed lack any genetic diversity. 

Here is a link (not safe for work) to a piece of artwork I made to provide you a mental picture of my notions of a hypothetical hermaphroditic human had Mother Nature otherwise gone that route or may still choose to go that route in the future before Man becomes entirely extinct should that be the fate for us. 

https://www.mediafire.com/view/94s6qklnc0xc3yx/concept_hermaphrodititc_human.png/file

 

My concept hermaphroditic human (the one that never happened but might still happen in the future) is conceived by me to possibly be able to both bear and sire healthy children under normal circumstances. The trouble is that uterine female mammals generally have limited physical strength and stamina. Since each and every of my theoretical hermaphroditic humans would have childbearing capability under normal circumstances, how well might they be able to do strenuous and dangerous labors? The non-childbearing men have a physical advantage over the childbearing women and therefore men have been assigned the more dangerous and difficult work for the longest time. Modern woke societal attitudes regarding sex and gender disregard such natural differences between men and women. But I digress. How might the hormones work in a single mammal's body with both impregnating and childbearing capabilities?  

 

 

I think a lot of it depends on the energy needed to create the next generation, the more energy needed often = longer living, more complex, life form's which normally would mean, a tiny mistake in just genetic copying would be eliminated by the complexity and energy needs of the lifeform. 

That is not present in less complex or energy dependent lifeforms, they have many more generation's to make up for the shortfall in genetic diversity, that two parents provide.

It's a balance, because of the time it takes for each approach to fill their respective niche in the world. 

Edited April 15 by dimreepr

[JohnDBarrow]

1 hour ago, dimreepr said:

I think a lot of it depends on the energy needed to create the next generation, the more energy needed often = longer living, more complex, life form's which normally would mean, a tiny mistake in just genetic copying would be eliminated by the complexity and energy needs of the lifeform. 

That is not present in less complex or energy dependent lifeforms, they have many more generation's to make up for the shortfall in genetic diversity, that two parents provide.

It's a balance, because of the time it takes for each approach to fill their respective niche in the world. 

The hermaphroditic animal species still involve two separate parents to bring forth young (at least in earthworms) as far as I know. Female parts of plants are above male parts, so pollination (inbreeding) won't occur within the same plant merely by the law of gravity. The wind (or birds and bees) has to carry pollen from neighboring plants for genetic diversity. Most plant life is hermaphroditic as far as I know. 

Edited April 15 by JohnDBarrow

[dimreepr]

Just now, JohnDBarrow said:

The hermaphroditic animal species still involve two separate parents to bring forth young (at least in earthworms) as far as I know. Female parts of plants are above male parts, so pollination (inbreeding) won't occur within the same tree merely by the law of gravity. The wind (or birds and bees) has to carry pollen from neighboring plants for genetic diversity. Most plant life is hermaphroditic as far as I know. 

Indeed, but how does that invalidate my point?

We are on a spectrum here, bacteria being the simplest and human's being the most complex, of course there's a crossover; much like wondering which line to pick at the checkout. 

[JohnDBarrow]

I wasn't trying to invalidate anything. I wanted folks here to understand that two separate individuals are involved in bringing forth young even in hermaphroditic species. 

For some reason, Mother Nature provided that the vertebrate (higher-level) animals be unisexual (male and female in separate bodies). Logically, I try to pick the line in the store that I perceive to get me out of the store the fastest. Mother Nature may have found it most efficient to put male and female in separate human bodies if nature has any free will or reasoning power at all. 

 

Another name for hermaphrodites are bisexuals.

This term is not to be confused with the sexual orientation of being attracted to both sexes. 

Edited April 15 by JohnDBarrow

[dimreepr]

10 minutes ago, JohnDBarrow said:

I wasn't trying to invalidate anything. I wanted folks here to understand that two separate individuals are involved in bringing forth young even in hermaphroditic species. 

For some reason, Mother Nature provided that the vertebrate (higher-level) animals be unisexual (male and female in separate bodies). Logically, I try to pick the line in the store that I perceive to get me out of the store the fastest. Mother Nature may have found it most efficient to put male and female in separate human bodies if nature has any free will or reasoning power at all. 

 

Another name for hermaphrodites are bisexuals.

This term is not to be confused with the sexual orientation of being attracted to both sexes. 

I think you'll find that folk's here, understand the nuance... 😉

[JohnDBarrow]

Human hermaphroditism might not be a good thing after all. That would mean each and every person could have a baby.  Even with male and female in separate bodies, the world is way overpopulated as it stands right now. 

[dimreepr]

9 hours ago, JohnDBarrow said:

Human hermaphroditism might not be a good thing after all. That would mean each and every person could have a baby.  Even with male and female in separate bodies, the world is way overpopulated as it stands right now. 

Overpopulated by whom?

Greenfly could overpopulate the world, if only they knew how...

[CharonY]

I think the discussion has veered off way into the speculation area. Several points are at best misconceptions. For example:

On 4/15/2024 at 6:49 AM, JohnDBarrow said:

For some reason, Mother Nature provided that the vertebrate (higher-level) animals be unisexual

This is inaccurate as certain fish species are hermaphrodites (and obviously vertebrates). 

 

On 4/15/2024 at 6:49 AM, JohnDBarrow said:

Nature may have found it most efficient to put male and female in separate human bodies if nature has any free will or reasoning power at all. 

 

10 hours ago, JohnDBarrow said:

Human hermaphroditism might not be a good thing after all. That would mean each and every person could have a baby.  Even with male and female in separate bodies, the world is way overpopulated as it stands right now. 

This is not how evolution works. Whatever has reproductive success will exist. A predominance of gonochorism in certain groups of organisms suggests that either a) it leads to higher reproductive success than hermaphroditism (under the given environmental conditions) or perhaps that b) there are developmental constraints which limits the conversion from one system to another.

Explanations for both have been proposed in a previous post.

[JohnDBarrow]

8 hours ago, dimreepr said:

Overpopulated by whom?

Greenfly could overpopulate the world, if only they knew how...

It is my notion that if all humans could have babies, not just half of the species, that would pretty much double our reproductive capacity. Men can fertilize women much faster than women can bear children. Women are only about half the population within the age group of human fertility. In unisex species, reproduction rate and baby-making efficiency are measured in the female, not male, half. 

Think about what our world numbers might be if our species was 90% women!

Edited April 16 by JohnDBarrow

[CharonY]

1 hour ago, JohnDBarrow said:

It is my notion that if all humans could have babies, not just half of the species, that would pretty much double our reproductive capacity. Men can fertilize women much faster than women can bear children. Women are only about half the population within the age group of human fertility. In unisex species, reproduction rate and baby-making efficiency are measured in the female, not male, half. 

Think about what our world numbers might be if our species was 90% women!

If that was the case, why is hermaphroditism not the dominant reproductive strategy?

[JohnDBarrow]

1 hour ago, CharonY said:

If that was the case, why is hermaphroditism not the dominant reproductive strategy?

PERHAPS, NATURE'S WAY OF NOT MAKING OUR OVERPOPULATION EVEN WORSE THAN IT IS ALREADY. 

Edited April 17 by JohnDBarrow

[CharonY]

42 minutes ago, JohnDBarrow said:

PERHAPS, NATURE'S WAY OF NOT MAKING OUR OVERPOPULATION EVEN WORSE THAN IT IS ALREADY. 

That is not how nature works. Nature does not follow any ideals or thinks ahead. Whatever works, works. If it leads to reproductive success it will stick around. If it doesn't,  it vanishes. You cannot think of nature like a planning entity and expect to be scientific about it.

[JohnDBarrow]

6 hours ago, CharonY said:

That is not how nature works. Nature does not follow any ideals or thinks ahead. Whatever works, works. If it leads to reproductive success it will stick around. If it doesn't,  it vanishes. You cannot think of nature like a planning entity and expect to be scientific about it.

It's just a human figure of speech. Even my science teacher in high school used the term "Mother Nature" as if "she" were some sort of living person. Sometimes human behaviors might lead to the outcomes of certain things and alter the future. We can select our sex partners at will. 

As to how and why the particular reproductive layouts of various living species came about, I can't honestly say. 

Edited April 17 by JohnDBarrow