Being mammals ourselves, it’s natural for people to be curious about the early history of our clade, and therefore, science writers had no trouble generating interest in the subject matter of two Nature papers this week describing two Jurassic creatures living at the cusp of mammalian origin.
The challenge came in encapsulating the news, since the two papers came to very different conclusions.
Both papers describe new fossils of squirrel-sized creatures of the group Haramiyida, an extinct branch on the evolutionary tree. One is a tree-climbing animal that the researchers conclude was a true mammal, implying that the haramiyida branched off after the origin of mammals. The other creature, however, was a ground-dwelling animal, complete with imprints of fur. It lived during the same era but does not qualify as a mammal thanks to a more reptilian type of inner ear.
Readers got a very different impression of the significance depending on which story they read.
Here’s how Laura Poppick started her story at LiveScience:
An extremely well-preserved rodentlike fossil recently discovered in China provides some of the best evidence yet for how the earliest human ancestors lived.
But if you read the Los Angeles Times, you’d see this angle from Brad Balukjian
Mammals first appeared 215 million years ago during the Triassic period, according to a new study in the journal Nature. Wait, no, they first showed up 175 million years ago during the Jurassic period, said another study in the same issue of the journal.
The LiveScience lede wasn’t particularly clear. Can you have evidence for “how mammals evolved”? You can have evidence for a theory describing how mammals evolved, or you can have clues or new data to help answer a question of how mammals evovled. Can you have "evidence" for a question?
But worse, the term “earliest human ancestor” seems inappropriate and bizarre. That phrase could be interpreted as the earliest members of the genus homo – the earliest ancestor that qualifies as human. If you interpret it as our earliest ancestor in the tree of life, obviously our lineage goes all the way back through fish, invertebrates, microbes, right to the common ancestor we share with all living things. I see no way early mammals could qualify as the "earliest human ancestor" by any science literate interpretation.
She does it again further down:
Martin and his team also believe both discoveries offer an important step forward in understanding the complexity and diversity of the earliest human ancestors.
What the…well, moving on….The LA Times lede better captures the conflicting nature of the papers.
In his version of the story, The Guardian’s Ian Sample led with one of the animals – a hook that seems more appealing to lay readers than whether or not the evolution of mammals has to be pushed back a few million years. This lede makes me want to know more:
The discovery of a small furry beast from the Jurassic era has given scientists fresh insights into the evolution of the first mammals on Earth. The fossilised remains of the squirrel-sized animal that plodded rather than scampered, came from rock dated to 165m years ago, when feathered dinosaurs shared the land.
He introduces the other animal and the contradictory nature of the papers further down.
Elizabeth Berber at the Christian Science Monitor took a similar approach in this story – starting with one of the animals:
Once, somewhere in what is now China, lived an animal with the fur and teeth – and poisonous spur – of a mammal, but with the ears and ankles of a reptile.
The poisonous spur resembles one on that amazing mammal the platypus. Her story also added a very helpful bit of background lacking in the other stories. Many members of the general public picture something linear when they think of evolution, so any time you can get people to picture a branching bush, it’s a big help.
Zhe-Xi Luo, a professor of organismal biology and anatomy at The University of Chicago and an author on the first paper, likens the evolution of mammals to a “vast bush” made of about two-dozen branches, the majority of which were “pruned in extinction.” Just three of those branches were spared natural selection's gardener’s shears and now form the three lineages of modern mammals.
At Nature, Sid Perkins has written a more complex story with a very nice lede that encapsulates the news:
Two fossils have got palaeontologists scratching their heads about where to place an enigmatic group of animals in the mammalian family tree. A team analysing one fossil suggests that the group belongs in mammals, but researchers looking at the other propose that its evolutionary clan actually predates true mammals.
Out of perverse curiosity I also checked with the “Intelligent Design” people would have to say. You can see one example here at Uncommon Descent. It’s too silly to bother critiquing on the Tracker, and not for those with senstive stomachs, but worth noting for the areas of public confusion that we science writers need to make sure we address. Just taking the spoon fed material on these stories isn’t enough – it really helps to step back and explain why the scientists' open questions over these details has no bearing on our broader picture of evolution.
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