Would humans outcompete sequential hermaphrodites?

Question

I want to have a species based on humans, where everyone is born as female, but switches gender to male later in their life. Assuming that transformation takes 4 years (*) hermaphrodite is born as woman, at 27 starts transformation and at 31 becomes man.

Assuming that anatomy of sequential hermaphrodites is equal as possible to humans, would humans outcompete hermaphrodites assuming same technological level in the stone age era.

Advantages:

• Nearly double population growth (humans have longer fertility window but it starts to drop after 27)

Disadvantages:

• Infertile during the transformation period
• Smaller number of physically strong soldiers
• Might be less willing to take risks, since there's no young men to do that

(*) I plan to ask is this realistic time period in separate question

Answer 1

Well, if this species is anatomically similar to humans, you have to consider one of our species' biggest design flaws: maternal mortality. In pre-modern times, it's estimated that up to one in twenty births resulted in the mother's death. If this is the same for your species, it's easy to imagine that for much of their history they will experience quite an unequal sex distribution among the population, as many women won't live long enough to make it into manhood.

But the other factor that skewed gender distribution in human history was warfare. In our species' history a big war would reduce the proportion of young men. In your species, there won't be any young men, so there's a question over who fights this species' wars instead. If it's the older men, then this would be a further factor that would reduce the proportion of men in the population. But my suspicion is that it would be young women and girls who'd primarily be press-ganged into military service. This might make your societies more apprehensive about fighting wars, as it's much harder to rebuild your population after losing a critical mass of your mating-age females than a similar number of mating-age males.

Once your species develops medical technology on a similar level to ours, the gender disparity is going to completely flip, as more women survive childbirth and more men live older lives. Your societies will face an unprecedented shift where the gender split goes from 60% female to 40% male, to 40-30% female to 60-70% male. For a civilisation completely unused to this, it would be fascinating to see what this sudden surplus of testosterone would do...

Answer 2

I'm going to go out on a limb here and say

Not if the hermaphrodites do it right

TL:DR: Don't assume that just because women can breed that they will try to.

Many other answers here are applying modern (or at the least, human) sociological values to an otherwise alien society. If this sexually hermaphroditic society develops a different approach to gender roles (or, more likely, the entire concept of gender) and adopts a more arbitrary caste based system, then you will quickly see similar roles to men/women developing but split along caste lines.

Strapping young girl? Military caste. Go forth, try your best to kill or be killed. Take risks. Don't breed, as death in childbirth is the worst shame a warrior can know. If you grow old enough to become a man then you have an awful lot of experience and can be used to train the raw recruits, not to mention stud the next generation of warriors into existence.

Likely to get killed in the first skirmish? Don't worry: There's always a need for the working caste. Feel free to breed if you want to, but don't expect any special treatment from the other castes. You're here to primarily support the other castes, including taking care of other people's children if required. If you grow old enough to become a man then bully for you.

Wide hips? Good pedigree? Mother has a history of twins? Breeder caste. You get food, protection and your pick of the men. You're likely going to die giving birth, but hey, at least you perpetuated the species. If you don't die and manage to live long enough to be a man then clearly you're good at this whole 'giving birth' thing, and the next generation could use some of your genetic material. Go forth and multiply.

This system requires more social interaction than the human system, and as such tribes can be expected to be more closely knit. If the death rates are similar to those of the human's you're trying to outcompete then you should come out ahead of the game (or at least drawing) by having specialised roles that are not gender specific, and as you'll likely develop specialties pretty quickly (your 'alphas' will likely be female, your wise men will be just that, you won't have any arbitrary traits defining social structure from the get go) your social structure may well pip humanity to the post and make up for any breeding disparity.

Plus it would make for a social structure that is simultaneously incredibly PC and hugely discriminatory.

Disclaimer: I mostly wrote this answer to be contrary. I have no idea if this would occur and, in fact, no way to simulate the social evolution of a pre-historic population, but it's a possible outcome!

Answer 3

The key human advantage is risk-taking

In human societies, men are generally less important to the reproductive process than women. Therefore men can be risked without incurring much risk to the population as a whole.

This is a powerful advantage for developing technology and for expanding through violence. Women, in general, had to reproduce to keep the species going; thus was true for all of history until the 1800 when improved nutrition and sanitation allowed many more children to survive. But men were never that necessary; one man can do the job of 10, so to speak, when it comes to making children. Therefore, an effective society will utilize its young men in high-risk, high-reward occupations to attempt to gain competitive advantage for that society. High-risk, high-reward things might include hunting dangerous things (like mammoth for food, or lions to keep them from eating your kids), long distance trading for valuable rocks from far-away places, or fighting your neighbors for prime land to steal their womens.

Risk taking humans can out-compete the more fecund sequential hermaphrodites in direct competition

So applying this principle to your sequential hermaphrodies, they are likely to be at a significant disadvantage in direct competition with humans. Sure they can reproduce faster due to having more women around, but if they fight battles, they have a relatively higher penalty for losing men in combat because there are proportionally less men. Each man lost in combat has relatively more negative effects on the ability of the society to produce children, compared to humans.

They also don't have the available expendable people to send out to do scouting or trading, unless the young women do this...in which case they are forfeiting their advantage in reproductive rate. Finally, it is worth pointing out, if combat is more or less concentrated in the males, the males of the sequential hermaphrodite would have significantly less experience with combat when they reach their 30s; and experience is the primary advantage of older men in combat and as combat leaders.

Answer 4

Can they breed with humans? Many scientists believe Neanderthals didn't go extinct but were absorbed through interbreeding with traditional humans. Given that your population has fewer men than women it's possible that the females of your species might interbreed with human males especially if your mails stay behind and the females go to war leaving their husbands behind perhaps for years.

As a side note I don't think this species population what really grow much faster than humans. Most human women continue breeding up till their thirties and some even up to their mid-forties men can continue breeding from puberty to their sixties. Whereas in your species the females only viable breeders until they reach 27 long before a human female would be still capable of breeding at this time. As for your men they are capable of breeding till 31. That's twenty-nine to 30 years of Lost potential when it comes to greeting. So in terms of population I actually think human population would be much higher

Answer 5

If life expectancy tables are correct, and the average life expectancy hovered between 20 and 30 for most of history, most of your females would not have an opportunity to live long enough to become a father. Since males would be rare, they would be much too valuable to risk in war. If we assume the average age of death is 30, and the people don't become fertile men until age 31, more than half of your population would not survive to reproduce as males. This would almost certainly remove the possibility of pair-bonding. A human couple can reproduce at age 14 or so, while among hermaphrodites, 14 is the age of the female, while 31 is the minimum age of the male.

If we are looking at human physiology as an analog, then most of the society would be females and thus on average be both physically weaker and less aggressive their human counterparts.

Humans would reproduce faster, be more aggressive, have more aggressive males to hunt, fight, and compete than the hermaphroditic society. They could tolerate more men being killed. Furthermore, human females could tend to the young while the men fight and hunt, while there could be no such division of labor in the hermaphroditic society.

Edit While infant mortality does skew the life expectancy statistic, it is undeniable that life expectancies were much lower long ago. Consider maternal death at childbirth. In countries where moms do not have access to quality medical care at birth, about 1 in 6 die in childbirth (Unicef note the rate is per birth, not over her lifetime.) This article does a good job at refuting the Live Science piece quoted in the comment. In it, the author cites age of skeletons in the catacombs.

if human lifespan had really not changed in 2000 years, then 35-year-olds shouldn’t have left their skeletons very often in the Roman catacombs. Unfortunately (for them), we find those 35-year-old bodies. A rough estimate (gleaned from tomb inscriptions that give ages) is that half of Romans who lived to age 15 – and therefore escaped juvenile mortality – were dead before age 45.

In a world where there is no antibiotics, no surgery, no dental care, no false teeth, no refrigeration, no stable food sources, and danger at every turn, death came quickly and often. A scratch could lead to sepsis. Food could turn in the hot sun and lead to food poisoning. Starvation, war, plague, and violence were constant companions.