The results of the study into the development of proboscideans show that the changes in the climate had a strong impact on the extinction of proboscideans long before humans migrated from Africa to other continents.
– However, we are not claiming that modern humans couldn’t have had a significant impact on the extinction of proboscideans in the later stages, says palaeontologist Juha Saarinen from the University of Helsinki, who participated in the research.
The study collected hitherto unseen amounts of data on the evolutionary adaptability of live and fossil proboscideans, including among other things the shape of skulls and lower jawbones, as well as tusks and molars, the structure of limbs, and body size.
The research carried out by scientists at the University of Helsinki in collaboration with the universities of Madrid, Bristol, Buenos Aires, and Berlin was published in the journal Nature Ecology and Evolution.
– Our data covers practically all the proboscidean species based on conclusive fossil discoveries over all of their evolutionary history, a total of nearly 200 species, says Saarinen.
Cooling climate kicked off decline in proboscideans
Proboscideans developed in Africa over 50 million years ago, and their evolutionary history was contained in that continent for some 30 million years.
Research findings show that the diversity of proboscideans grew more varied as they spread from Africa to Eurasia some 20 million years ago, and to North America a little later (about 16 million years ago). Their adaptation is visible especially in the specialisation of skulls and teeth to process different food sources.
The diversity of proboscideans reached its peak around five to ten million years ago, at the latest, after which it has declined as the climate has cooled down, grown drier, and gained more variation. Adaptable species like our modern elephants were best able to adapt to the changing climate, as features such as their durable and efficient dentition made it possible for them to access many kinds of food sources.
– The spread and world-wide success of modern humans was probably a significant factor in the plight of the elephants during the last wave of extinction that started around twenty-thousand years ago, which led to the extinction of e.g. the Woolly Mammoth, says Saarinen.
– It is also clear that the alarming decline among the three remaining species of elephant – the African forest elephant and bush elephant, and the Asian elephant – is caused by poaching and other human activities.
CNN's news article about this topic:
https://edition.cnn.com/2021/07/02/world/mastodons-elephants-climate-change-scn/index.html
Reference to the article:
https://www.nature.com/articles/s41559-021-01498-w