Odd usage that: “Males” with “wives.” As Colin Barras puts it at New Scientist?:
Three has become five. Laetoli in northern Tanzania is the site of iconic ancient footprints, capturing the moment – 3.66 million years ago – when three members of Lucy’s species (Australopithecus afarensis) strode out across the landscape.
Now something quite unexpected has come to light: the footprints of two other individuals.
It has been all too tempting to interpret the original trackways – often reconstructed as belonging to two adults and one juvenile – as evidence of a prehistoric “nuclear family”.
More.
Now, the rumor is that the Australopiths might have been polygamous, though we have no idea of the identity of the other two walkers (sister? ) (aunt?) (adult daughter?). Yes, that is speculation but so is all the rest.
Buried several paragraphs below the social media noise is the question of whether this group walked like modern humans or not. That could be important in addressing any claims about tem at all.
Okay fun, let’s move on:
From Helen Briggs at BBC:
“The footprints of one of the new individuals are astonishingly larger than anyone else’s in the group, suggesting that he was a large male member of the species.
“In fact, the 165cm stature indicated by his footprints makes him the largest Australopithecus specimen identified to date.”
…
“A tentative conclusion is that the group consisted of one male, two or three females, and one or two juveniles, which leads us to believe that the male – and therefore other males in the species – had more than one female mate,” said Dr Marco Cherin, director of the school of paleoanthropology at the University of Perugia.
The claim is that their social structure was more like that of gorillas than chimpanzees. 
From Charles Q. Choi at LiveScience:
These footprints — a kind of ichnofossil, or trace fossil — reveal that this extinct species may have had major differences in sizes between the sexes. This difference, in turn, suggests that the species might have been polygynous, where males have multiple female mates, the researchers said. Previous research suggested the fact that polygyny leads to a few males monopolizing all females leads to intense competition between males, which favors the evolution of larger males that can better deal with their rivals.
Let’s study 500 “Lucy” era households on each side and see.
See also: Researcher: “Lucy” died falling from tree
Our ancestors more gorilla than chimp?
The search for our earliest ancestors: signals in the noise
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