But Macchiarelli insists the femur belonged to a quadrupedal ape, not a bipedal hominin. It's an important distinction. Before the discovery of Toumai, it had long been believed that humankind originated in Eastern Africa. Toumai solidly roots the human family tree on the western side of the continent. But if it turns out not to be a hominin, evolutionary history shifts again.
2. Out of Africa
Homo sapiens originated from a single, common ancestor that lived in Africa 300,000 years ago. Then, 100,000-80,000 years ago, Homo sapiens began to spread across the world.
Our African origins have been demonstrated countless times by genetic analyses and fossil evidence.
But what's known as the multiregional model has persisted. Its proponents suggest modern humans don't have a single origin but evolved independently of each other from different pre-human populations. Asians originated from the Asian Homo erectus, Europeans from the neanderthal man, and Africans from the African Homo heidelbergensis.
It's a theory ripe with racist undertones and support has ebbed in the past few decades.
Those who backed the model pointed out that modern Asian populations and Asian Homo erectus had unique shovel-like incisors. This was seen as a sign of common ancestry.
In April, the final nail was hammered into the theory's coffin. Genetic analysis showed that this trait of the incisors was merely a side effect of adaptation to a cold environment. The gene that controls the shovel-like incisors also coincidentally decreases the number of sweat glands and enriches mothers' milk with fat. These features can be crucial for survival during an Ice Age.
Because of these traits' genetic connection, Homo erectus and Asian modern humans would have incidentally evolved similar incisors by evolving them against cold in a parallel manner. So the shovel-like incisors were not inherited by Asian Homo sapiens from a Homo erectus ancestor but acquired because of the cold environment.
3. A seriously big dinosaur
We've long known that gigantic dinosaurs roamed ancient African landscapes. The Paralititan, from Egypt, weighed about 60 tonnes. Giraffatitan, from Tanzania, was among the tallest; another Tanzanian specimen, Tornieria, was among the longest. The meat-eating Spinosaurus, found in Niger and North Africa, was even bigger than Tyrannosaurus rex.
But when and where did gigantism among dinosaurs first evolve? Ledumahadi mafube, from South Africa, sheds some light on this question.
The 200-million-year-old dinosaur weighed about 12 tonnes and was the first to pass the 10-tonne threshold.
4. Reimagining reptiles
Mammals evolved from an unexpected source: reptiles, and specifically a group of "mammal-like reptiles" called the cynodonts.
One of the biggest differences between mammals and reptiles today is their reproductive biology. Most reptiles lay eggs and show little to no parental care, whereas most mammals give live birth to younglings and provide them with extensive parental care.
We hadn't known if cynodonts were more like mammals or reptiles in this respect - until 2018. Scientists in the US studied the fossil remains of an adult cynodont dating back 190 million years, and found preserved with it the skeletons of 38 babies.
That's a huge clutch size; one that's never encountered in mammals but is typically found among some reptiles that lay eggs. The scientists also argue that it's unlikely the mother cynodont could have provided enough milk or parental care to raise so many babies.
This suggests cynodonts must have had a reptilian reproductive biology. It also means South Africa's fossil record, which has been interpreted to propose that cynodonts cared for their young, might need a reinterpretation.
5. A four-legged find
In June, it was announced two species of fossil amphibians new to science had been found in South Africa. They are the oldest evidence of four legged land-dwelling animals, called tetrapods, in Africa: a missing link between fish, amphibians and reptiles. Historically, the search for tetrapod ancestry overlooked Africa. This puts it on the map when seeking evidence for how the transition of life from sea to land occurred.
• Julien Benoit, Postdoc in Vertebrate Palaeontology, University of the Witwatersrand
- The Conversation
