By Gavin Mackintosh-
Analysis of teeth dating back 200 million years suggests that the earliest mammals functioned like reptiles – leading less active but much longer lives.
The research, led by the University of Bristol and University of Helsinki in Finland, is the first time palaeontologists have been able to study the physiologies of early fossil mammals directly.
Researchers used X rays to scan fossils of teeth from two of the earliest mammals, Morganucodon and Kuehneotherium, which roamed the earth alongside early dinosaurs. Scientists said they were able to literally count the rings
Researchers also studied growth rings in the tooth sockets that could be counted to reveal how long the animals lived.
The results, published in Nature Communications, indicated a maximum lifespan of up to 14 years for the animals. This is much older than their similarly sized furry successors such as mice and shrews, which tend to only survive for a year or two in the wild.
Dr Elis Newham, research associate at the University of Bristol, said: “We made some amazing and very surprising discoveries.
“It was thought the key characteristics of mammals, including their warm-bloodedness, evolved at around the same time.
“By contrast, our findings clearly show that, although they had bigger brains and more advanced behaviour, they didn’t live fast and die young but led a slower-paced, longer life akin to those of small reptiles, like lizards.”
Dr Pam Gill, senior research associate at the University of Bristol, was inspired to use advanced imaging technology on the teeth after a colleague had a tooth removed.
They told Dr Gill they wanted to get their tooth X-rayed, as it could reveal information about a person’s life history.
“That got me wondering whether we could do the same to learn more about ancient mammals,” Dr Gill said.