Did Australopithecus africanus evolve into Homo habilis?

I'm wondering if anyone can explain the process by which Australopithecus Africanus evolved into Homo habilis and then from there into Homo erectus. Secondary to that, why do evolutionary biologists think these protohumans became extinct?

why do evolutionary biologists think these protohumans became extinct?

"genus is like a make of car".
All Toyotas are more closely related to each other than to any other make of car, and theyre all derived from the original Toyota,which was made in the 1930's". He adds "A grouping make up of all four wheel drive cars made by Toyota would make a sensible genus"
Wood says/"But a grouping of four wheel drive cars made by different companies would not qualify, even if they look sorta alike and drive alike, since they dont have the same common ancestor"

Secondary to that, why do evolutionary biologists think these protohumans became extinct?

Yes, humans and Neanderthals had sex. And they gave us an STD.
To be fair, we may have given them diseases that ultimately led to their extinction.

But it does tell us a lot more about human history, and can give us insight on how exposure to disease has shaped human evolution. STDs have been around since the dawn of humanity. Herpes may have first infected our ancestors more than a million years ago. Syphilis has been around since at least the Middle Ages. It’s possible STDs are what encouraged humans to stick to monogamous pairings.

“The real big picture is that our history, our evolutionary history is a lot more complex than we thought 5 to 10 years ago,” Pimenoff says. The fact that we interbred with other species can explain how humans acquired new genes after leaving Africa. But it’s important to know that viruses can drive our evolution as well. “And our history, is also the history of our pathogens.”

Pimenoff hopes to continue to study this to answer another big answer about HPV: Why does it clear up in some people very quickly, and linger and cause cancer in others? “We don’t know why in some people, the immune system naturally clears it,” Pimenoff says. Depending on your genetic background, and on the particular strain you’re exposed to “there could be a different to how your immune system reacts to an HPV infection,” he says. (The best prevention for HPV-related cancers right now, he says, are the widely available vaccines.)

Pimenoff’s study also raises questions about what happened to the Neanderthals. If we contracted HPV from them, what did they get from us? It’s possible that humans spread diseases that brought about their extinction. In April, researchers at Cambridge and Oxford Brookes universities published a paper that suggested Neanderthals may have been particularly susceptible to germs that cause stomach ulcers and herpes.