It wasn't easy being a hominoid millions of years ago.
Some of our early ancestors didn't just have to worry about big cats and deadly snakes.
They may also have been attacked and eaten by birds, according to new research that may also solve the mystery of who killed a young child in southern Africa about 2.5 million years ago.
Ever since it was discovered in 1924, the famed Taung Child -- as the skull came to be known -- has puzzled scientists.
The prevailing theory has been that a large cat killed the kid, believed to have been 3 years old at the time of his death.
But anthropologist Scott McGraw of Ohio State University says he has a better idea.
Raptors, he says, or more specifically the African crowned eagle, was the likely perpetrator.
McGraw and his collaborators have spent years trying to piece together the story of predation on monkeys and other apelike critters on Africa's west coast.
Some of the story is pretty well established. Leopards are the main predators, but chimps also attack smaller monkeys.
But McGraw has long suspected that some of the animals that preyed on our early ancestors were airborne.
That's tougher to prove, he says, so for the last 20 years he has spent much of his time collecting bones from in and around eagles' nests to see how these powerful birds go about their business.
The Tai rain forest in the Ivory Coast is an ideal location for the research because "the entire predator system is still intact," McGraw said.
So the same types of predators are there today that once preyed on some of our distant relatives.
McGraw's lab includes an extensive collection of monkey skeletons that he acquired in Africa over the years as part of his general research into primate behavior.
More recently he teamed up with Susanne Schultz of the University of Liverpool, who spent two years monitoring 20 eagle nests in the Tai Forest and collecting bones from the nests and from the ground below.
By comparing the bones from the nests with the reference collection in McGraw's lab, the researchers were able to show that eagles indeed had a taste for monkeys.
The monkey skulls, for instance, show puncture wounds that were caused by an eagle's powerful talons or beak.
Oddly enough, the monkey most favored by the eagles is the mangabey, which is fairly rare, and, unlike all the other monkeys in the forest, spends most of its time on the ground.
It's also the largest of the monkeys.
That's counterintuitive, McGraw points out, because a smaller monkey in a tree would seem to be an easier target for an eagle than a bigger monkey, which can weigh up to 25 pounds, on the ground.
"So here we've got an airborne predator that seems to be specifically targeting an animal that is found at relatively low densities, and on the ground, and is also the biggest," McGraw said. "So these eagles are not only capable of killing a large, ground-dwelling primate, but they routinely do so, and they do so in frequencies much higher than you would predict by chance."
McGraw says his evidence doesn't prove that the eagles actually killed the monkeys.
They could be scavenging them after they are killed by something else. But he says he's seen enough eagles go after monkeys to convince him they are the killers, not just the scavengers.
Further research now under way in his lab may prove that.
He's also pretty sure he has the answer as to who or what killed the Taung Child.