Back in the mid-1970’s … most of this article was common knowledge.
The Earth was cooling and drying … and so the jungles were becoming forests, and the forests were becoming open savanna, with open fields between forests becoming bigger and bigger… and the perfect place for predators to lie in wait!
In jungles, unless you are on a well worn path, you could wait days waiting to see the prey… but if your timing was off, the prey got to hide in some obscure part of the jungle… and lunch time was over!
But in the open terrain … with tall grasses… what a person needed was height! He needed an angle that the predators didn’t have. He might also need to cooperate with some other hunters … travel in packs … to better defend against surprise attack.
So the only NEW thing in this article is the discussion of ionization; here’s a key text:
"A paper published today in the Journal of Geology makes the case: Supernovae bombarded Earth with cosmic energy starting as many as 8 million years ago, with a peak some 2.6 million years ago, initiating an avalanche of electrons in the lower atmosphere and setting off a chain of events that feasibly ended with bipedal hominins such as Homo habilis , dubbed "handy man."
"The authors believe atmospheric ionization probably triggered an enormous upsurge in cloud-to-ground lightning strikes that ignited forest fires around the globe. These infernos could be one reason ancestors of Homo sapiens developed bipedalism – to adapt in savannas that replaced torched forests in northeast Africa."
The writer wants to suggest that upper atmosphere ionization promoted significantly more forest fires… and this was part of what was clearing the plains of hiding places for humans to exploit.
Frankly, I like the theory. But even before electrons we had “cooling and drying” … and nobody really complained about that as a constraint!