by the age of 4 or 5 a child was expected not only to amuse themselves independently, but also babysit for younger siblings
This is certainly what you see in pictures from all around the world, including the UK only a few generations ago.
I'd also take issue with this:
Dr. Barry Hewlett has covered research on infant touch in his book Diverse Contexts of Human Infancy and whereas in traditional societies babies are held or touched approximately 98-99% of the time
Because I've also read this in an article on Mongolian Breastfeeding:
Then I moved away from Canada, to Mongolia, where my husband was conducting a wildlife study. There, babies are kept constantly swaddled in layers of thick blankets, tied up with string like packages you don't want to come apart in the mail. When a package murmurs, a nipple is popped in its mouth. Babies aren't changed very often, and never burped. There aren't even hands available to thrust a rattle into. Definitely no tummy time. Babies stay wrapped up for at least three months, and every time they make a sound, they're breastfed.
And given how easily I, who have no anthropology expertise can remember an exception, I can't help but think that that blanket statement is rubbish (at least in cold countries!)
I'm a computer programmer. Working around a baby is doable. Working around toddlers and kids means that you are definitely ignoring them to look after themselves for a lot of the time. I'm not saying that's bad, but it's not motherhood the way it's sold to us these days. And that's the case if your job is weaving, spinning, pottery or breadmaking too - the job requires some concentration and can't just be put down when your child wants something - just think of the babies strapped to women's backs in the fields - sure, they're attached to their mum, but their mum is hardly paying them attention, it's not some golden childhood experience.