> There are different kinds of bipedalism.

Sure, but limb development is highly canalized even in quadrupeds. You have to look at this scenario from the paradigm of the selection pressure which started our lineage on the trajectory towards bipedalism, and it very clearly extends far back beyond the earliest signal of even the Australopiths. A change in a trait like major skeletal morphology takes an extremely long time to fix.

> Early homo were unable to run even if they were obligate bipeds.

I’m going to push back on this. It’s too confident a claim for the physical evidence base, which is scarce. Unless some major work was released and I haven’t heard about it, which I feel is unlikely because I attend most seminars from the major anthropogenic institutions like CARTA and Leakey.

> Nuchal ligaments, Long bone length, gait, narrowing of the hip, extension of the achilles tendon and arched foot, broader heel and short toes. I’m unsure of any others off the top of my head. These traits would have appeared around 1.8mya

All of these have a pretty clear developmental trajectories extending far back beyond erectus. Australopith tibias are notably elongated.

> It very well might be that we just evolved a kit that could be repurposed for a hunting style - and we’re misunderstanding the cause and effect.

This is basically “just so” stories in a nutshell.