2023-08-15 00:09:00
A new study from the University of Helsinki reveals a stark example of how changing environmental conditions drive evolution. In this case, it is elephant teeth.
Experts have found that the evolutionary course of proboscideans – the group that includes today’s elephants and their ancient relatives – has been largely influenced by climate change over the past 26 million years in East Africa. .
In particular, experts have identified spurts in the evolution of teeth in elephants around 10 million years ago that coincided with major climate changes.
Food evolution
For thousands of years, the vast landscapes of East Africa have witnessed transformative change. Among them, the cheek teeth of proboscideans stand out as a testimony to adaptability.
These elephants, along with their ancestral counterparts, have altered their diets in response to changing vegetation patterns and the climate of their habitats.
Evidence suggests that some proboscidean lineages, such as choerolophodonts, began adopting grass-rich diets 23 to 11 million years ago, much earlier than previously thought.
This dietary evolution finds a marked period regarding 7 million years ago in the Lake Turkana region of East Africa. Here, the thriving savannahs – drier and full of grasses – became the main feeding grounds for the first true elephants.
Study the evolution of elephant teeth
“This confirms the hypothesis of these regions as ‘species factories’ where evolutionary adaptation to changing environmental conditions first centered around them,” explained the study’s lead author, Juha Saarinen.
Grasses, loaded with grains rich in minerals called phytoliths, pose a daunting challenge. These grains lead to significant wear of the teeth.
However, choerolophodonts from the Lower and Middle Miocene periods managed to adapt to these herb-rich diets with only minor changes to their dental structures.
Transformative changes
Fast forward to around 10 million years ago, and a major climatic upheaval reshaped East Africa. True elephants, or Elephantidae, have undergone a deeper dental evolution.
Their teeth, especially the molars, saw increased crown height and more ridges.
“We were able to show that the strongest drying peaks of the East African climate over the last 7 million years correspond to evolutionary surges in the increase in the height of the dental crown and the number of ridges on the molars, whereas these evolutionary changes did not reverse during periods of less harsh climatic conditions,” Saarinen said.
“This confirms previous suggestions that adaptive traits of organisms are adaptations to extreme rather than average environmental conditions. »
What the researchers found
A comparative analysis of elephant vegetation and diets over the past 7 million years has revealed an increasing dominance of grassland habitats and grass-eating elephants with complex dental adaptations. Yet this trend saw a change regarding 100,000 years ago.
Likely due to large global climatic fluctuations, only the modern African savannah elephant, with its less specialized teeth, has survived in East Africa.
Implications of the study
A similar ecological adaptability may explain the survival of the Asian elephant in Asia. Meanwhile, the African forest elephant has found refuge in the forest territories of central and western Africa.
“The ecologically quite versatile modern elephants were the only survivors of the tumultuous climatic changes of the late Pleistocene,” Saarinen said.
“Now it is us humans who are threatening the last surviving species of this ecologically important group of animals, and we must work hard to prevent them from ever becoming extinct. »
The research is published in the journal Nature.
Learn more regarding proboscideans
Proboscideans are a group of large mammals that includes elephants and their extinct relatives. They are characterized by a long trunk (or “proboscis”), large tusks and a massive body. Here are some key points regarding proboscideans:
Existing species
Today, there are three extant (or currently living) species of elephant: the African bush elephant, the African forest elephant, and the Asian elephant.
Mammoths & Mastodons
They are two of the most famous extinct relatives of modern elephants. Mammoths were more closely related to the Asian elephant, while mastodons were a separate lineage.
Physical characteristics
The trunk is a notable feature of proboscideans and is a very versatile organ used for breathing, smelling, grasping, and making sounds. Their tusks, which are elongated incisors, can be used for digging, lifting, picking up food, and as weapons.
Elephant teeth and their diet
Most proboscideans are herbivores, eating mostly grass, leaves, and fruit. Their molars are adapted to grind hard plant matter.
social behavior
Elephants, living representatives of proboscideans, are known for their complex social structures. Female elephants and their young live in tightly knit family groups led by a matriarch, while adult males may roam more independently or in small bachelor groups.
Conservation
Elephants are currently threatened by habitat loss, human-elephant conflict and poaching for their ivory tusks. Efforts are underway to conserve these magnificent creatures and their habitats.
Evolution
Proboscideans have a rich fossil record that dates back millions of years. Throughout their evolutionary history, they exhibited a wide range of sizes, from small-bodied Palaeomastodon to gigantic imperial mammoths.
Distribution
While today’s elephants are restricted to parts of Africa and Asia, proboscideans once roamed a much wider range, including North America, Europe and other parts from Asia.
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