It's important to note that the author of this paper is a social anthropologist, not a biologist or similar...

From the actual paper, in case you didn't, you know, actually read it:

My analysis emphasizes the inconclusiveness of existing models for the human species through a transdisciplinary inquiry including evolutionary anthropology, human behavioral ecology, genetics, paleoanthropology, nutritional sciences, obstetrics, biological and cultural anthropology, classical ethnography, and feminist and gender perspectives in the social sciences.

You're right, she does seem quite unfamiliar with biology. Damned obstetricians and their voodoo magic. Why can't they study biology like other doctors?

Any paper that presents a different hypothesis needs to show why the established one is wrong, the OP paper doesn't.

But the author wasn't claiming that existing ones were wrong. She writes in the paper you linked to (emphasis mine):

In textbooks, you find the same hypothesis you already find in Darwin’s Descent of Man: size dimorphism is the result of an increase in the size of males due to sexual selection occurring via combat between males, as it is for gorillas or elephant seals [2]... My analysis emphasizes the inconclusiveness of existing models for the human species..

So, your claim that she's presenting a different hypothesis and not an additional hypothesis is clearly a straw-man. Did you even read the article?