Elephant ancestors´ teeth evolved in response to long term changes in diet and climate in Africa | University of Helsinki
In marked contrast to the childish creationists superstition that a magic supernatural man in the sky created everything as is, including Earth itself, about 8-10,000 years ago, two research palaeontologists at the University of Helsinki, Finland, have shown that the proboscideans, which includes modern elephants, their ancestors, and ancient relatives, evolved their teeth in response to environmental changes in East Africa over a period of between 20 and 7 million years ago.
They have published their findings, open access in the Journal, Nature Ecology & Evolution.
As we have come to expect, there is not a hint in their research that elephant teeth are the result of anything other than an evolutionary process, driven, as the Theory of Evolution predicts, by environmental change. There is never a hint that magic played any part in the process.
As the University of Helsinki news release explains:
The latest study about of proboscideans (elephants and their ancient relatives) from the University of Helsinki provides proof that some proboscideans started to adapt to locally grass-rich environments in East Africa first by changing their behavior and starting to feed more on grasses. This happened in some lineages of proboscideans, such as choerolophodonts, much earlier than has been thought until now, about 23 to 11 million years ago in parts of East Africa.Technical detail is given in the paper in Nature Ecology & Evolution:
Also, around 7 million years ago in the lake Turkana region, increasingly grass-rich diets of the earliest true elephants were associated with dryer and more grass-rich savanna environments than elsewhere in East Africa.This supports the hypothesis of such regions as “species-factories” where evolutionary adaptation to changing environmental conditions first centered around.
We were able to show that the strongest peaks of drying of the East African climate during the last 7 million years (for example about 4 and 2 million years ago) correspond with evolutionary bursts in the increase of tooth crown height and the number of ridges on the molar teeth, while these evolutionary changes did not reverse during periods of less harsh climatic conditions. This supports earlier suggestions that adaptive traits in organisms are adaptations to extreme rather than average environmental conditions.
The ecologically quite versatile modern elephants were the sole survivors of the tumultuous climate changes of the late Pleistocene. Now it’s us humans that threaten the last surviving species of this ecologically important group of animals, and we should work hard to keep them from being lost forever.
Assistant Professor Juha Saarinen, first author Department of Geosciences and Geography
University of Helsinki, Helsinki, Finland.
Feeding on grasses is more demanding on teeth than feeding on most other kinds of plants due to a high content of mineral grains called phytoliths in their leaves, causing heavy abrasion on teeth.
Nonetheless, during the Early and Middle Miocene the choerolophodont lineage of proboscideans were able to shift to more grass-rich diets with relatively modest changes in the morphology of their teeth.
Since about 10 million years ago, major changes in climate had a more profound effect on the evolution of proboscidean teeth in East Africa, especially the evolution of true elephants (Elephantidae) with highly specialized high-crowned, multi-ridged molar teeth.
Comparing evidence of past vegetation and the diet of elephants during the last 7 million years also showed an increase of grasslands and increasing dominance of grass-feeding elephants with highly specialized teeth throughout that period in most parts of East Africa. However, during the last 100 000 years this situation changed probably because of drastic fluctuations in global climate and eventually only the dietarily more generalist modern African savanna elephant (Loxodonta africana) with less specialized teeth survived in East Africa. Ecological generalism might similarly explain the survival of Asian elephant (Elephas maximus) in Asia, while the African forest elephant (L. cyclotis) was able to find refuge in more forested parts of Central and Western Africa.
AbstractA very clear example of how the teeth of African elephants evolved over time in response to changing environment and changes in the availability of food. Some species evolved to the point where they could not adapt to more change and so became extinct - hardly the work of an intelligent designer.
Identification of the selective forces that shaped adaptive phenotypes generally relies on current habitat and function, but these may differ from the context in which adaptations arose. Moreover, the fixation of adaptive change in a fluctuating environment and the mechanisms of long-term trends are still poorly understood, as is the role of behaviour in triggering these processes. Time series of fossils can provide evidence on these questions, but examples of individual lineages with adequate fossil and proxy data over extended periods are rare. Here, we present new data on proboscidean dental evolution in East Africa over the past 26 million years, tracking temporal patterns of morphological change in relation to proxy evidence of diet, vegetation and climate (aridity). We show that behavioural experimentation in diet is correlated with environmental context, and that major adaptive change in dental traits followed the changes in diet and environment but only after acquisition of functional innovations in the masticatory system. We partition traits by selective agent, showing that the acquisition of high, multiridged molars was primarily a response to an increase in open, arid environments with high dust accumulation, whereas enamel folding was more associated with the amount of grass in the diet. We further show that long-term trends in these features proceeded in a ratchet-like mode, alternating between directional change at times of high selective pressure and stasis when the selective regime reversed. This provides an explanation for morphology adapted to more extreme conditions than current usage (Liem’s Paradox). Our study illustrates how, in fossil series with adequate stratigraphic control and proxy data, environmental and behavioural factors can be mapped on to time series of morphological change, illuminating the mode of acquisition of an adaptive complex.
Saarinen, J. & Lister, A.M.
Fluctuating climate and dietary innovation drove ratcheted evolution of proboscidean dental traits.
Nat Ecol Evol (2023). https://doi.org/10.1038/s41559-023-02151-4
Copyright: © 2023 The authors.
Published by Springer Nature Ltd. Open access
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)Fig. 3: Trends in proboscidean dental traits in relation to aridity.
a–d, Evolution of hypsodonty (a), number of lophs/lamellae (b), enamel thickness (mm) (c) and enamel plicae frequency (d) in East African Proboscidea 26–0 Ma. Symbols for species are as in Fig. 1; colours mark families or paraphyletic ‘gomphothere’ group (blue), with each icon representing one molar. Lines connect mean values of each taxonomic group per locality and are for visualization. e-f, Aridity proxies: mean ordinated hypsodonty values of proboscidean localities (locality symbols are as in Fig. 2) (e), aeolian dust accumulation data from cores 659 and 722 (f). g–i, Example photographs illustrating morphology and measurements of molars in lateral and occlusal views: crown width (W) and height (CH) (hypsodonty = CH/W) (g), loph/lamella (L) and loph distance (LD) (h), and enamel thickness (ET) and plicae (PL) (plicae frequency = number of plicae in 1 cm of enamel band) (i). Left, P. macinnesi (Gomphotheriidae) m3, Maboko, Kenya (NHMUK-PV-M15541a). Right, P. recki recki (Elephantidae) M3, Kanjera, Kenya (NHMUK-PV-M15418, reversed). Photographs are not to scale. The photographs on the left (Protanancus) represent a more plesiomorphic elephantoid molar and those on the right (Palaeoloxodon) represent a derived elephant molar. HYP, hypsodonty. Specimens photographed at the Natural History Museum, London.
And of course, no sign that the scientists thought the Theory of Evolution was inadequate for explaining the observable evidence, with several strands of evidence, including climatology, supporting the theory that changes in elephant dentition over time were evolutionary changes, driven by environmental changes.
And all happening several million years before Earth existed, according to creationist superstition!
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