Humanlike thumb dexterity may date back as far as 2M years ago

We still are the first cells that lived.

From a cell's point of view, there are no ancestors.

All old world monkeys and apes have opposable thumbs. Some of them still live in trees. So, leaving the wood and hunting by throwing stones does not seem reasonable to me as a reason for thumbs. But maybe I did not understand what is meant by “we”, hence my question.

You should give yourself more credit, you just haven't practiced enough.

If you spend half an hour straight on throwing practice, you'll get quite good at it.

I think it was also a law of large numbers game. With teamwork we'd all be throwing rocks simultaneously at the same target. Also the practice component that the other poster mentioned

I think you are measuring yourself on the wrong scale. Sure you might be less precise than some other humans, but clearly you are way better than a horse, or a wolf or many other animal who might be basically incapable to throw things.

Is this all really throwing specific? Don't punching, hammering or other biomechanic also benefit from this? I'm not arguing the anatomy, just the "rock throwing" part.

I mean, throwing a rock might come in handy from time to time.. but it seems insufficient to be a driving force.. to me. Spears maybe.. We even have evidence of neanderthal spear making... but that's 1.5m years later.

You can make a living with a spear. Feeding a family by hunting birds with rocks seems near impossible. Seems like much less of a game changer than clubs, spears, digging sticks, etc. I can imagine a population dependent enough on these to create evolutionary pressures.

This is not an educated opinion... just a layman's speculation.

Meanwhile, I also suspect that hunting plays a bigger role than currently fashionable. Chimps are basically bound to live where figs grow. They need a variety of fig trees, because different varieties fruit at different times. No figs, no chimps. Their diet defines their range.

Most modern foraging cultures rely heavily on food plants that require processing: cooking, soaking, pounding, grinding.... We're not very good at digesting plants. Even chimps aren't great at it.

Assuming earlier ancestors were chimp-like, I think they had to have widened their diets beyond fruit... That means either meat or harder to digest vegetables.

Paranthropus (a divergent family of human-like species) do seem adapted to a wider vegetable diet. Their skull was crested, like a gorilla, to facilitate gnawing on uncooked roots, leaves & such. Homo & Australopithecines don't have such features. It just doesn't seem as likely that we evolved the ability to eat a wider vegetable range than chimps, and then regressed to a narrower range again.

The invention of fire is often referred to as "an external digestive system." You don't really need this for meat. Fresh meat is digestible. Even chimps can eat fresh meat, and we're more carnivorous than chimps. I think cooking, and other processing methods reintroduced us to vegetarian diets.

It's actually really surprising that we don't know what these early species ate. For most animals, diet defines lifestyle. A species that hunts or scavenges for most of its diet is subject to totally different pressures than a fig eater.

“Stoning” as punishment and a means of (slow, painful) execution seems consistent with this

Technology is rarely usurped entirely. I definitely agree that rock throwing in fights still exists, and people will do it when necessary. It's not, however, a primary method of warfare or 1-on-1 conflict... outside of specific circumstances like defending walls. Maybe a situation where one side has armour and swords and the other has numbers. Even then, long term, I'd wager on the the former.

Hunting methods tend to perpetuate. I'm not saying that no one ever hunts birds with rocks. I'm sure many people do. I'm equally sure that very few ever fill the pot this way.

For rock throwing to have shaped our arms from Habilis to Erectus,

A just want to say that I'm not arguing against any core parts of the theory. Hand/thumb articulation. Shoulder biomechanics. Explosive/elastic ability. There's plenty of evidence for that. There are also plenty of alternative ways to theorize how this was useful.

I think rock throwing is the popular explanation because it assumes the least behavioural complexity. It could have been more complex behaviour, like spear throwing. We only have evidence of stone tools because composition. But, I think it's safe to assume that this represents a very small part of the Erectus (even habilis) tool repertoire.

If I had to accept rock throwing, my theory would be "alpha scavenger" behaviour, like brown bears. Rock throwing is be pretty useful for chasing large predators off their kill. This is an extant "hunting" method, stealing from lions. Cultures that still do this (now for cultural, more than nutritional reasons) use nothing but bravery. They walk in, projecting confidence. Lions retreat, at least temporarily. The people cut off a haunch and walk away. A crude stone knife/axe (the one tool we know was widely used) is an essential tool for this. You need to butcher super fast, before the lions regroup and try to recover the kill.

That'd be an evolutionary advantage. Lions & bears do this, but it takes a lot of body mass. If a band of 50kg animals can chase off a pride of 150kg animals or a single 250kg animal... this is very efficient. Usually being alpha scavenger requires a tradeoff: large, calories consumptive body size in exchange for access to calories.

Hard way to make a living, but at least plausible.