It's society & available materials.

If you took all your knowledge 10k years ago the daily life would still fairly resemble the lives they had.

That's a beautiful way of thinking about it!

My grandmother passed away in 2015, but when she was born in 1922, there were Civil War veterans and people who had been owned as slaves still walking around. She was 43 when the Civil Rights Act passed

That's not to say that some of these cities weren't huge though. Rome had ~750K at it's peak. Some places in China had 1 million. We just have a lot more huge cities now.

https://www.worldatlas.com/ancient-world/the-largest-ancient-cities-ever-built.html

Our entire economic system is built upon this, too. The idea that people other than the ultra wealthy can just retire and... not work when they get old for example (retirement funds are biggest shareholders of publicly traded corporations btw).

Developed countries are seeing the damage of growth stopping and we haven't done much to mitigate it. Productivity per worker is, of course, way up luckily - but so are people's lifestyle expectations. If we all wanted to live like they did in ancient Greek times (minus the pillaging of neighboring countries I guess), we wouldn't even need many workers. But people want so many things that didn't exist 100 years ago, let alone 2+ millennia ago.

For now, we could just solve this by importing more workers from 3rd world countries still experiencing growth. Slow down their economic growth and our decline. But people are racist and don't want to.

The good news is, once those 3rd world countries have strong enough economies, they'll also stop producing babies as retirement plans as has been the case historically (you'd have like 8 or 9 kids so you can live on the family farm while they do all the work - when the economy gets better, you stop doing that).

The advent of agriculture (11.5 kya) was 4.5 hectomothers ago

I came here to say "obviously American, anything but metrics...", but you bet me to it.

Surprisingly no. At least in central and western Europe, child marriages were very much a nobility thing. Securing alliances and such. And even for those the first child may well have been much later.

I don’t have an individual statistic on hand but https://fakehistoryhunter.net/2026/01/18/age-of-marriage-giving-birth-in-medieval-europe/ has collected a bunch of sources that suggest that the usual age of first marriage in medieval Europe for women was around their mid 20s, pretty much the same as today.

Lots of babies and children died before adulthood though, so its actually not a bad bet for 25 as an average birthing age for one that survives to adulthood. Not that every woman would lose her first 2 kids or whatever but enough certainly did to drive the average up somewhat from what it would be with modern medicine.

Tbf, it was also far more common for people to have a shitload of kids, which takes time and thus would mean the mother was a fair bit older for the youngest few. My grandma was the youngest of 12 and her mother was well into her 40s when she was born.

Can confirm. My great grandma told me she got married at 18 which made her an "old maid" at the time

But they don't have a single kid, so the average age when giving birth is maybe higher

Actually, this math is almost exactly how the young earth creationist cult came to their number for the age of the earth. The counted out all the begats in the Bible from Adam to Jesus and multiplied by an average amount of time between births.

Exactly. The fact that our kids can look different from us at all is fucking wild

What kind of evolution can you expect in 450 iterations?

Actually quite a lot. The pace of evolutionary change is a function of the amount of variation present in a population and the intensity of selection (i.e. the death rate). There was one study done of the variation of bone dimensions present in modern populations of chimpanzees that suggests that the transition from chimpanzee-style locomotion to full bipedality (at least the variant of bipedality observed in Ardipithecus (~5 million years ago) could have happened on the scale of a few thousand years.

This is not to say that it did happen that fast, just that it could have given a strong enough intensity of selection. There is a weird tendency in paleoanthropology for researchers to propose something that might have happened and it becomes accepted by the general public as something that did happen.

First law of socio-genetics: Celibacy is not hereditary

From some book of Murphy's laws I found at home as a kid and fell in love with

Similarly: we all come from an unbroken line of people who had children.

indeed we come from an unbroken line of animals who had offspring. you can hop back one generation at a time til you get to our early ape ancestors, then those shrew-like things, reptiles, fish, then single cell organisms, in the end you'll reach the very first cell to ever exist, one single cell from which every living thing evolved.

Not just people, it goes back all the way to the origin of life, whether that happened here or elsewhere and life just somehow ended up migrating here.

There's an unbroken hereditary line between each of us and cells that first tried to eat mitochondria and instead of breaking them down into one meal's worth of energy and nutrients, they ended up forming a symbiotic relationship, giving our ancestors (and us) the ability to take more energy from the oxygen that was slowly filling the atmosphere than it was causing damage and surviving the earliest known mass extinction as well as snowball earth.

Then our lineage was able to survive the Cambrian explosion, I'm guessing that's than brains evolved and suddenly life could control a wide variety of different shapes and body types and it did before settling in to the more common body types that survived to this day.

We survived countless mass extinctions, including all of the major ones, like massive asteroid impacts that rained molten glass all over the globe just from the rebound and made today's global warming seem quaint. Each of our ancestors was able to survive to the age of reproduction without getting eaten by the giant insects of the Carboniferous (though we were still in the water so kinda lucked out), we survived the early oceans/seas, the emergence of amphibians and reptiles. We survived the dinosaurs, probably as tiny nocturnal rodents. We survived past that when birds and mammals diversified after the dinosaurs were gone.

We survived when primates started changing the very nature of the game of survival, despite several other species getting a head start on populating the globe. For better or worse, we took the planet from Neanderthals, homo erectus, the Denisovans, the hobbit-like hominids, and any others that left Africa before us (not to mention dominated the competition inside Africa).

Only at that point did we start surviving the brutal history of our species and all the wars, famines, plagues, natural disasters, building collapses, personal disagreements that could have turned violent, religions, brutal rulers, collapses of civilization, and emergence of the next set of bandit or war lords.

Also billions of years of single-celled competition prior to that mitochondria symbiosis event.

You're assuming that your matrilineal line is entirely composed of firstborns.

Mathematically it's a lot. Realistically a lot of those ancestors end up being common after 4-6 generations.

Kings tend to have shorter lifespans, though, what with other people wanting to be king, or for someone else to be king instead of the current one, or for there to just not be any king at all...

That's a lot, but also not. I know my grandmother and know of her mother but beyond that no idea who they were beyond where they were from.

We assume my ancestors are all from the same place (Alligator rivers) but going back that far it just seems so slim we're not from elsewhere too