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[deleted] OP t1_iuyx79v wrote

[removed]

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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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