'breeding individuals' Population collapse.

[placemats]

It's an interesting read, but what popped out to me was the phrase 'breeding individuals'. This would, in my thinking have meant that the females survived but very few men did, because there needs to be more women than men to ensure population survival.

https://www.theguardian.com/science/2023/aug/31/population-collapse-almost-wiped-out-human-ancestors-say-scientists

Perhaps they got a bit confused

I don't think that's likely. In a one-off disaster the number of men could get very small, but this is a period of more than 100,000 years; over that timescale the sex ratio is certain to be close to 50/50, because evolutionary pressure won't allow it to diverge by much.

The use of "breeding individuals" just means that given the data they have, they couldn't rule out a typical population of (say) 2,000; only 1,300 of whom reproduced. There could well be a sex imbalance here, e.g. more females than males reproducing.

Only females can reproduce to birth and beyond, i.e give live birth and feed. The men may well have died from some virus or disease, not necessarily war or famine, but some would survive.

I always thought that evolutionary pressure due to a collapse was because of a virus, and females are better at fighting viruses.

It doesn't say anything about the sex ratio - it's just looking at the total effective population size of breeding adults - men and women together. So excluding children, the elderly and adults who didn't have children.

The sex ratio would probably have fluctuated over time, but no reason to think it was consistently biased one way or the other.

The population collapse lasted 100,000 years, i.e. for 4,000 generations. Even if males in one generation disproportionately died due to an illness or other event, the sex ratio would quickly be restored through reproduction.

Even if viruses were a factor, we don't generally see large sex differences in deaths from epidemics. Women in societies without birth control tend to be constantly pregnant or breast-feeding, so are often relatively undernourished and so more vulnerable to disease.

Men who have offspring are included in the 'breeding population'.

The population sex ratio is likely to be close to 50/50 because of Fisher's Principle.
https://en.wikipedia.org/wiki/Sex_ratio#Fisher's_principle

Do men have any idea of how many children they have? Certainly women do.

You only need two males to ten women to produce a healthy brood. Male children tend to die more than female children.

Putting a 19th/20th/21st century outlook on it scuppers the research.

Breeding individuals are those of either sex to be of reproduction age so puberty to menopause for women, puberty to death for men.

Males typically, even now, die younger than females; from birth, infancy, childhood, puberty, adulthood and older.

The problem is that the language has been so corrupted that ‘breeding individuals’ could plausibly mean women or it could mean the entire population- one result of messing around with language is that it becomes confused.

If breeding individuals consisted of several males and one female, how would the population increase?

There are known archaeological sites throughout the world that supports a female/male imbalance in favour of females, more so than the 51f/49m percentage. Those sites had communal living and an agrarian way of life.

Today, in certain communities, there's an imbalance of male to female ratio in favour of males.

From my limited understanding of these matters, males would be at far higher risk of premature death from violence because male humans are usually more aggressive than female humans, more likely to take risks and possibly more likely to be out hunting than hanging around the camp/base looking after children, gathering food and so on. So there might not have been all that many adult men around, but on the other hand, the male's involvement in reproduction takes a few seconds, so that wouldn't matter all that much.

If you just want randomly to make up stuff that fits your own preconceptions, OP, why bother quoting a research paper in the first place?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3367790/

Lots of highly contentious possible interpretations of this, but sex ratio is affected by crisis conditions, namely famine:

'The study identified an abrupt decline in sex ratio at birth between April 1960, over a year after the Great Leap Forward Famine began, and October 1963, approximately 2 years after the famine ended, followed by a compensatory rise between October 1963 and July 1965.'

What are my own preconceptions?

I'm merely discussing the language used within a catastrophic event, worse than any pandemic, the flu pandemic of 1918 killed more men than women, despite women being close in together in factories at that time.

You concluded that the paper means that "the females survived but very few men did". Which is does not say or imply.

You have then tried to back that up with data about 51:49 sex ratios in homo sapiens societies. A 51:49 ratio, even if it were relevant to the different species studied in the research, is not evidence that "very few men survive". It's evidence of totally the opposite - that sex ratios remain finely balanced.

And then we get into totally woo stuff like, "you only need 2 males to 10 women to produce a healthy brood". Obviously you'll be able point us to all those thriving societies with 1:5 male to female ratio...

I think they can tell sex ratios of those able to pass on their genes in the past based on analysis of different types of DNA. E.e.8000 years ago the proportion of men passing on their DNA plummeted (1 man for 17 women) and no-one knows why for certain https://psmag.com/environment/17-to-1-reproductive-success. But that was a single event.

The fact you can manage with two men to ten women doesn’t mean that’s all there was for 4000 years.

The article says nothing about sex ratio in the small population. All that stuff is speculation by readers here.

Breeding population just means adults who can potentially reproduce. It's used in population studies of animals n the exact same way.

I don't think it's difficult to imagine why this could be. Nature is dangerous and unchancy. I remember reading about a modern group of hunter-gatherer people in the Amazon, a tribe which was consistently on the bring of collapse. All adults needed to be consistently focused on producing and supporting as many babies as possible in order to keep the adult breeding population at a sustainable level, due mainly to disease and other dangers.

I can't imagine life was much easier for many prehistoric peoples.