Museum researchers are using fossil mammoth molars from across Europe, northern Asia and North America to study how tropically-adapted animals changed to the woolly mammoth of the late ice age. Their findings provide a model for the process by which new species originate.
Fossils from the Quaternary ice ages provide excellent opportunities for tracing the origin of new species through time.
The fossil record of this period:
In other words, we can use it to observe evolution in action. The lineage leading to the woolly mammoth provides one of the best examples of this.
Woolly mammoth tooth.
The mammoth’s ancestors arose in Africa, and were tropically-adapted browsing animals closely related to the living elephants.
Around 3 million years ago, they spread into the northern hemisphere and began a process of transformation leading to the highly-specialised woolly mammoth of the late ice age, adapted to cold, treeless environments and a diet of grass.
We have traced this process of transformation in most detail using fossilised molar teeth.
By measuring samples of fossil mammoth molars from dozens of localities across Europe, northern Asia and North America, we have been able to chart an increasing adaptation to a tougher diet.
Molars showed an increase in:
By comparing fossils between different regions and time intervals, we have also shown that the process of change involved at least 2 transitions involving the origin of new species.
In particular, it appears that the first major step in the origin of the woolly mammoth occurred in China as much as 2 million years ago, while the final changes took place in north-east Siberia about a million years later.
In both cases it is plausible that the changes were driven by known changes in climate and vegetation.
It has become clear that the process by which species originate involves a complex pattern of individual populations evolving, migrating, interbreeding with each other, and in some cases dying out. The net process over time is one of changing morphology.
We are collaborating with colleagues in Germany, Sweden, the US and the UK to investigate the evolution of the woolly mammoth using ancient DNA. This technique is used extensively to study mammoths.
We have mapped the reduction in genetic diversity that led up to the mammoth’s extinction, which may have contributed to its ultimate demise. We have also shown how one genetic group, originating in North America, spread over a period of 40,000 years of the last ice age to replace populations in Siberia and ultimately Europe.
With our collaborators we are currently investigating the possible role of hybridisation in the origin of Late Pleistocene mammoth populations, and the origin and spread of genes adaptive to the ice age environment.