Early mammals lived fast and died young
66 million years ago, a meteorite wiped out the dinosaurs and three-quarters of the planet’s plants and animals. However, some mammals survived and evolved into large beasts, filling the niche left by their Jurassic ‘fellows’. The panodonts, large herbivores that emerged about 66 million years ago, are the first group to emerge among them. Their relationship to later mammals is unclear, as is their incredible evolutionary success – they diversified into a wide range of forms, though they became extinct around 34 million years ago, in the late Eocene. Now a new study seems to have found the key to their survival: they lived fast and died young. The conclusions have just been published in ‘Nature‘.
In this studio, Gregory Funston, Steve Brusatte and his colleagues, from the University of Edinburgh (United Kingdom) point out that they have discovered through dental analysis of fossil remains from the site in the Badlands National Park, South Dakota (USA), that the first large mammals after dinosaurs grew twice as fast as modern dinosaurs of equivalent size and had a comparatively shorter lifespan. To find out, they used different methods, such as dental trace element mapping, to shed light on the life history of the pantodon. Pantolambda Bathmodon, who lived 62 million years ago.
It is a strange mix between dog, pig and bear, with robust limbs (bears), a large and deep torso (pigs) and a face with a short snout and a long tail (dogs); although, it did not look anything like any of them: they weighed about 42 kilos, and they were born quite developed, reaching puberty in about 3 or 4 years, and dying after a decade of life, more or less. These were placental mammals, which, unlike marsupials (such as kangaroos, whose young grow in a pouch), or monotremes (such as the platypus, which hatch from an egg), placental young do most of their work. its early growth inside the mother, facilitated by a specialized placenta that nourishes and cleanses the baby.
Most of the individuals at the site studied were between three and four years old when they died. However, the oldest was eleven, which is consistent with half the life expectancy of an animal of that size today (about 20 years). The authors believe that the strategy of being born so large would have ensured greater survival; on the other hand, the fact of reaching maturity so soon would have allowed a higher rate of reproduction in the species, which would have been an evolutionary success at least during that period.
Then, it could have become a disadvantage, as they would be competing with other species that might need fewer resources (being smaller and living more ‘slowly’) to survive.