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[deleted] OP t1_iuyx79v wrote

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atomfullerene t1_iv02ftn wrote

>They didn't have the dramatic gender dimorphism of humans

Hm? Humans have less sexual dimorphism than the other great apes, and H. erectus had more sexual dimorphism than humans (but not as much as other apes)

https://www.nature.com/articles/s41598-019-44060-2

>and were about half again as big as humans

H. erectus were larger than previous hominids but they weren't larger than modern humans! If anything they were marginally smaller.

>Did they have a monthly reproductive cycle like in humans or was it seasonal?

Very few primates have seasonal reproduction, so we can guess this is similar to humans and other primates

>How long did it take them to reach sexual maturity?

It's not entirely clear but H. erectus seems to have matured a little faster, or at least grown a little faster

https://royalsocietypublishing.org/doi/10.1098/rstb.2015.0234

> (humans reach this in about a dozen years though the ability to carry a child successfully and safely to term can take another few years)

Age of first birth tends to be around 19-20 in modern hunter gatherers. It's around 15 in chimps, so H. erectus was probably somewhere in the range between the two, though I couldn't find actual data for it

> homo erectus would likely have been able to have children faster than the 1 year average people tend towards.

This is not a realistic birth spacing, for humans or H. erectus. Hunter gatherers show a birth spacing of 3-4 years, and the other great apes have longer birth intervals. It's only in sedentary societies with abundant food and no need to carry offspring while foraging that humans can come close to a birth rate of 1 per year, and it's unusual even then. Actually producing 15-30 babies is even more unusual.

I wouldn't expect H. erectus to produce any more offspring than modern humans. Probably a bit fewer actually, considering the way modern humans displaced other hominids and seem to have had higher populations when they did so.

https://www.jstor.org/stable/10.1086/667591 table 1 has birth interval and age at first birth data

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Cannie_Flippington t1_iv1d7oa wrote

>Humans have less sexual dimorphism than the other great apes

Compared to H. Erectus, it's dramatic... at least until 2020. I see I'm behind the times.

>they weren't larger than modern humans

Where am I getting my science these days, smh...

>This is not a realistic birth spacing

It's not. I was unclear, I see. This is the average length of time between one birth and the conception of the next. Humans are physically capable of getting pregnant immediately after birth but unlikely to do so for roughly six months. Add in the six months it takes for the average length of time for conception and you've got a year. This was looking at the maximum number possible, rather than what's probable, because everything is pure speculation anyway.

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cremecherries t1_iuzgx1r wrote

In the second line, you mentioned 'larger size' even though you mentioned they were half our size? Were you comparing them to primates?

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ILoveADirtyTaco t1_iuzigeg wrote

“Half again” means 1.5X so they were quite a bit larger than Homo sapiens

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DodgerWalker t1_iuzwgsz wrote

Is that a regional phrase? I figured that’s what it meant from context, but not something I’ve heard someone say before (I live in the USA). Much more common would be “one and a half times” or “50% larger.”

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Psychological-Rip291 t1_iuzx8wg wrote

A more common version of it is "half as big again", and is definitely common in non-american English at least

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Cannie_Flippington t1_iuzx9yx wrote

Am US but I've been told I use weird phrases and words and my spouse inexplicably is offended by my pronunciation of orange.

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ballisticks t1_iuzxrx9 wrote

How do you pronounce orange differently?

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dharma_curious t1_iv0a9ln wrote

Not OP, but if he's anything like my buddy, I'm assuming or-ang. Like the or from and/or and ange like the nickname for someone named Angela or Angie.

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WallabysQuestion t1_iv06lgl wrote

“Half as big again” is completely acceptable but how on earth do you say orange?!

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muskytortoise t1_iv06otc wrote

Your post is top voted yet it's pure speculation with a few facts thrown in not even relevant to your guesswork. Assumption of the 1 year between pregnancies is based off modern diet and even during modern times in societies that prefer large families is an exception rather than the norm. As another poster mentioned, humans typically take longer than a year and other apes tend to have longer, not shorter times. The 15-30 seems like a very high estimate to the point where there are no undisputed records of more than 44 and anything above 20 being quite literally unique events on a global scale. Theoretical limit is neither what OP asked for nor practical to consider given that it's virtually never achieved even in conditions of resource abundance. Those are outliers. For most ape species it seems that the child mortality is below 50% suggesting that the numbers you mentioned are not only unnecessary to maintain the species but also would be an huge unsustainable strain on the resources available. The number would feasibly comparable to pre-industrial humans and other apes, so at minimum three and unlikely to be more than 10.

https://www.eva.mpg.de/documents/Elsevier/Hill_Mortality_JHumEvo_2001_1556100.pdf

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjXzMS6j5T7AhXHxIsKHXFlBb8QFnoECA4QAQ&url=https%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fam%2Fpii%2FS0047248418301283&usg=AOvVaw3bRuYVEs9iCVTL0ywOLE-Q

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Cannie_Flippington t1_iv1bbxa wrote

Yeah, I suppose OP was asking about averages and not most physically possible. Also your second link cause me physical pain.

And your post is just as much speculation as we have no idea the lifespan or how long homo erectus would remain fertile in that lifespan. You're also not considering the high infant mortality rates where many mothers had 10 children or more historically but only some would survive to adulthood. Not to mention lack of birth control - we have no idea what their mating practices were that functioned to avoid over saturating their environment, if any.

In short, I said we've got no idea and your comment supports that.

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muskytortoise t1_iv2tumt wrote

We know of ancient humans and modern era apes and for the most part the time between births is regulated by the same mechanisms and the death before adulthood is at about 50%. Speculating that a species evolutionarily closer to us is somewhere between us and species that share a common ancestor with us and them both is a reasonable guess. Your speculation throwing out numbers like up to 60 children per lifespan (completely unheard of among any apes) while claiming that there is no possible way of knowing was a lot less reasonable than mine.

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Cannie_Flippington t1_iv3227t wrote

We can't prove or disprove it with our current knowledge. Educated guesses are still guesses and 60 might be very unlikely (just as 30 is for homo sapien) it's still within the realm of possibility for such wildly speculative topics such as this. The realm of possibility tends to be extreme.

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kidnoki t1_iuzdlee wrote

We have a lot of this data, good questions, but I've read a lot of data on this, and it's much less ambiguous. Just wish someone would have cited it...

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gwenzillaaaa t1_iuztu23 wrote

i thought humans didn't have a lot of sexual dimorphism?

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DodgerWalker t1_iuzwqu1 wrote

Humans are usually much easier to tell whether they’re male or female at a quick look than say a dog or a horse, which you’d pretty much have to look at their genitalia to tell. So yes, humans have high sexual dimorphism.

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Cannie_Flippington t1_iuzy2lu wrote

Men tend towards larger upper body size, heavier musculature, larger overall skeleton, higher quantities and more locations for body hair, etc.

Women tend towards lighter frames, larger hips, gozongas, less body hair in fewer places, etc.

Men and women even store fat differently after puberty with women storing it more subcutaneously (better insulation for the baby cooker) and men storing it more around their vital organs (bad for your long term health but good for protecting your organs in combat).

Fun fact though... higher estrogen in women and higher testosterone in men has a similar effect on the vocal cords, making the voice deeper. Men get that deep bass like Vin Diesel and women get that sultry husky voice like Scarlett Johansson.

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FreeGothitelle t1_iv00wg0 wrote

Correct, we even lost a lot of our sexual dimorphism compared to our ancestors we share with apes.

As humans we're obviously biased to see every minute difference among our own species now, so people may assume otherwise.

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Practical_Cartoonist t1_iuzsdmo wrote

> and it's due to our similarly high rate of chromosomal abnormalities in our zygotes)

I don't understand the connection between this and menstruation. Why does a high rate of chromosomal abnormalities favour menstruation?

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Cannie_Flippington t1_iuzxrrd wrote

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3528014/

>Hypothesis 2: Spontaneous Decidualization evolved for embryo selection
>
>A more recent idea, with experimental support, argues that SD evolved to allow the mother to sense embryo quality upon implantation. Teklenburg et al. [24] used a human co-culture model to study the interaction between decidualizing ESCs and blastocysts and found that ESCs trigger a strong response against impaired embryos but only upon differentiation into decidual cells. These authors argue that SD evolved to compensate for the high rate of chromosomal abnormalities in human embryos, allowing the mother to limit her investment in bad embryos. In support of this hypothesis, the same group showed that women with impaired decidualization responses are not able to sense embryo quality, evidenced by increased fecundity but also recurrent pregnancy failure [25].

It's not the only reason, but it is likely one of the reasons behind why humans menstruate so frequently. It's a waste of resources so there would ostensibly need to be some sort of evolutionary pressure that makes it a valid expenditure. Prioritizing your best embryos and discarding less than ideal ones minimizes nutrient loss rather than find out later after a significant time and resource investment that you've got a nonviable pregnancy.

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ARX7 t1_iuzt171 wrote

With no background, I'd expect it would be due to the nature of non-viable zygotes being 'rejected' so menstruation would need to be more frequent to eventually have a viable zygote.

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AlternativeFilm8886 t1_iv0bmoy wrote

I see people often drawing comparisons between homo-erectus/habilus; neanderthals; denisovans, and "humans", but shouldn't they be compared with homo-sapiens? Are they not all species of humans?

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joshuas193 t1_iv0lxps wrote

I was just looking it up and the internet says that H. Erectus could be over 6 feet tall.

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GaussWanker t1_iv0mv5c wrote

Wouldn't more developed at birth also imply a longer gestational period, so even if the baby is weaned and semi independent still takes as long to have another child?

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Cannie_Flippington t1_iv17dhi wrote

Not necessarily. Cows and humans both gestate for 9 months and yet baby cows are fully precocious and many times larger than a human infant.

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garry4321 t1_iuyily0 wrote

For almost any mammal the rule is number of nipples/2 = average amount of kin/birth, with # of total nipples being the average maximum per birth minus rare outliers. Therefore just like humans, the average birth is 1 child with max generally being 2 (triplets extremely uncommon)

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AlyssaJMcCarthy t1_iuynmy2 wrote

Im pretty sure the question is not asking how many kids per pregnancy, but rather total kids over a lifetime.

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Warpedme t1_iuyviwy wrote

That's totally not what I got it of the post but I'm also much more interested in the answer.

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kidnoki t1_iuyxhk5 wrote

Yeah you'd have to consider optimal fertility cycles and mating/seasonal habits and tendencies. I remember looking at a birth rate chart for the months and we had a very cyclic pattern going, where there would be heavy births after colder months and an obvious 9 month barrier, that would decrease fertility, but obviously this was just the most common, we have pretty crazy reproductive options compared to some of the larger more social and intelligent mammals. Probably because we domesticated, which throws in a whole new set of pressures on birth cycles.

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MisterBilau t1_iuywdnd wrote

Lol, come on, that's obviously not the question. Of course they mostly had one child per pregnancy, with the occasional twins / triplets. Why would anyone think otherwise, or even ask.

The question is how many children the average homo erectus would have, not how many children per pregnancy. I would say it must have been higher than current numbers (so, higher than 2 per couple), probably quite a bit higher, to account for extreme child mortality - otherwise populations would dwindle fast.

I'd be very surprised if it was less than 4 per couple or something.

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M0nsterjojo t1_iuym03e wrote

Now I want to state the exceptions to this (NOT being hostile, just for anyone that's curious) would be something like a large ruminant stomach grazer (Which has 1 offspring per 4 nipples) and pigs/dogs which can have litters upwards of < 1 nipper per child.

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DumbDekuKid t1_iuz2mky wrote

Estimates between 2 and 6: https://www.researchgate.net/profile/Kit-Opie/publication/236143885_Grandmothering_and_female_coalitions_a_basis_for_matrilineal_priority/links/0deec51656f4d3b9ea000000/Grandmothering-and-female-coalitions-a-basis-for-matrilineal-priority.pdf?origin=publication_detail

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BadgerSilver t1_iv0020i wrote

This has to be due to infant mortality. I can't imagine they weren't just having sex and getting pregnant whenever they could

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muskytortoise t1_iv0dzxx wrote

Humans are somewhat unique in that we can have children at any time of the year. Pregnancy and live children cause hormonal and social behaviours reducing chances of another conception for a time - pregnancy and feeding are both very energy intensive. Infant and child mortality tends to be about 50% for most ancient humans, apes and most large mammals with some exceptions. 6 children over a lifetime is about the replacement rate with those numbers, and most populations tend to keep at mostly a steady population level otherwise they would run out of resources. Given that they did not outcompete humans by their sheer numbers, about replacement rate sounds like a very reasonable assumption to make.

So what exactly are you basing your assumption off of?

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alderhill t1_iv0knc3 wrote

I don't think it's clear that homo sapiens and homo erectus overlapped, and if so, we certainly do not know about all locations.

H. Erectus did stick around for a long time, even as new homo species branched off, but my understanding was the evidence for overlap is slim outside of Africa. Maybe Indonesia, but I've seen conflicting evidence.

In any case, they were mostly already on their way out by the time we started showing up in numbers.

Neanderthals and Denisovans of course did overlap with us in some regions.

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AChristianAnarchist t1_iv0myet wrote

The evidence for overlap outside africa is pretty overwhelming actually. There have been more examples of this overlap found in the middle east and asia than in Africa.

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muskytortoise t1_iv0oxp2 wrote

While you are absolutely right to point it out I didn't mean they were directly competing with humans but rather pointing out that constant breeding much above replacement rate would allow them to outcompete other groups. Since tendencies describe averages, if they had more than 6 children at the typical 50% mortality rate it would cause the population to grow fairly fast. Of course that comment probably stemmed from greatly overblown idea of infant mortality that person has.

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alderhill t1_iv0qkir wrote

OK cool, yea, I got that point, just was a bit confused about the context of homo erectus. I agree, though. It seems biologically, primates just generally aren't super-breeders.

IIRC, earlier homonids probably came to breeding age quicker than we do (under depending on nutrition, etc)., so a Homo erectus female of 10 years may have already been in prime mothering age. A child every 2-3 years or so would mean that by age 30, she'd possibly be a grandmother and done with most child rearing.

I do agree as well that mortality rates are on average overblown... once they pass the first two or so tough years, their odds are much improved

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BadgerSilver t1_iv7m3wu wrote

Humans will have babies every 1-2 years consistently if fertile with unprotected intercourse. Are you saying homo erectus is that different?

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The_Dread_Salami t1_iv0j105 wrote

It's also possible they had a breeding season i mean most babies now are concieved between june and November as is. Then there's the fact that jealous males in other species kill any child they don't think is there's, this may also be a contributing factor.

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mcr1974 t1_iv0lbf3 wrote

September is the month with most births, which would suggest most conception takes place in December?

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The_Dread_Salami t1_iv0ns7m wrote

It's too cold to hunt very often aside from big game that'll keep because of the cold which left plenty of time to "keep warm" so I can easily see this being accurate for our early ancestors too.

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atomfullerene t1_iv2ujtg wrote

Birth spacing in hunter gatherers is 3-4 years, and it's the same or higher in great apes. Generally speaking, they all tend not to get pregnant while still nursing the previous offspring.

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BadgerSilver t1_iv7k5hg wrote

I don't believe it, we're no different from hunter gatherers in capability of having yearly offspring. In religious communities where I grew up, most families had kids spaced ~2 years apart, and they had access to birth control. Nursing hormones don't outright block pregnancy for 4 years. I bet we can find a study

edit: from the NHS "Most couples will get pregnant within a year if they have regular sex and don't use contraception". We can safely assume this applies to hunter gatherers. This 4 year thing is absurd.

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atomfullerene t1_iv7u0u2 wrote

Nursing frequency and birth spacing in Kung hunter-gatherers

citation for long birth intervals in !Kung

Foraging and Menstruation in the Hadza of Tanzania

citation for shorter, but still 2.5 yr birth intervals for Hazda

Analysis of Factors Involved in Lactational Amenorrhea

citation for big variation in how long infertility lasts during nursing, depending on specific situation...in other words, you can't safely assume that the same thing applies to people with totally different nursing habits and totally different nutritional profiles.

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[deleted] OP t1_iuz29xg wrote

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[deleted] OP t1_iuzd0h7 wrote

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[deleted] OP t1_iuzc9ky wrote

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5GCovidInjection t1_iuzcvnv wrote

Following up on what the others said, I have to wonder what infant mortality rates were like for early human species. If, like Neanderthals and modern humans, there were species coexisting, probably mortality rates were similar given the time context.

We didn’t dramatically cut infant mortality worldwide until the 20th century or so for modern humans.

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rainawaytheday t1_iv0b6wi wrote

A big difference is the further back you go, you get a much larger birthing canal and babies carried in a longer term. So we have bigger, older, healthier babys being born easier, with less potential complications.

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PefferPack t1_iv0mx1f wrote

Yeah but think about how foul society was as it was forming. Population density without medical technology was what was so dangerous. Would be a good approach to look at tribal infant mortality (50% sounds high to me).

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Ok-Championship-2036 t1_iv0nwr7 wrote

So, I can't answer for the whole genus. However, if you're referring to neolithic hunter-gatherers, we know that they COULD have children roughly every 2 years (if they could feed it) and that small family units traveled in 3-6 people. Very small, close units of direct family. We know this because foraging had to be done on the move, so childbearing was limited by your ability to carry younger children (0-2).

If you're referring to early agricultural communities, this differs greatly. We know that early agriculturalists were creating their own labor force. So probably as many kids as possible. This is the part of the archaeological record where we begin to see bone pathology tied with over-birth. Specifically, women who have died from constant birthing or are otherwise impaired/limited to this job function. This brings the life expectancy down 9 years compared to hunter-gathering (life expectancy roughly 23yo) and we begin to see a lot of malnourishment too. Because their diets begin to lack biodiversity and relying on starch vegetables causes cavities.

source: anthropologist

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