African savannahs which cover more than a third of the Earth’s surface emerged 10 million years earlier than scientists once thought, a new study has revealed.
Soil studies and anaylising how grasses use photosynthesis to create energy have shown, says the study, the savannahs probably emerged 20 million years ago.
The study may even have a bearing on how man evolved and learned to walk upright.
Popular theory is that man’s prehistoric ancestors only left behind theit ape past when the forests disappeared and they had to walk on the grasslands.
But study head Dr Thomas Lehmann explained: “Our findings can also have an impact on the interpretation of human evolution.
“The ‘cradle of mankind’ was probably surrounded by grasses.”
Scientists from the Senckenberg Society for Nature Research, in Frankfurt, Germany, say their study debunks earlier theories on Africa’s development.
Until now. they say, it was widely believed that equatorial Africa was covered in dense forest between about 15 and 20 million years ago.
Scientists also believed that the savannah’s C4 grasses only appeared about eight to ten million years ago
But now, says the study, they believe the grasslands are around twice as old as once thought.
Dr Lehmann – from the Senckenberg Society for Nature Research and the Natural History Museum in Frankfurt – said in a statement obtained by Newsflash: “Today’s savannas are dominated by so-called C4 grasses.
“Due to their special metabolism and their effective photosynthesis method, they are well adapted to hot, dry habitats with high levels of solar radiation.
“It is assumed that C4 grasses were formed around 30 million years ago – the oldest fossil evidence from Africa to date, on the other hand, has been dated to only around 10 million years.”
The international research team studied fossil sites from the early Miocene era from around 20 million years ago in Kenya and Uganda.
They carbon dated soil organic matter, fossil soils and plant wax biomarkers, and combined the results with their phytoliths analysis – small particles of silica that survive well in most soils and sediments in distinctive shapes.
Lehmann said: “Our result throws the previous theories on the emergence of the dominance of C4 grasses overboard.
“In our new study, we can show that locally extensive C4 grass landscapes were already there 21 to 17 million years ago, [which are] comparable to today’s savannas.
“We assume heterogeneous habitats ranging from forests to sparsely wooded grassland.
“Our data pushes the earliest evidence of C4 grass-dominated habitats in Africa – and globally – back more than 10 million years in Earth history.”
Lehmann explained that the dispersal of C4 grasslands in East Africa is linked to important adaptations in prehistoric mammals.
He added: “For example, the development of high-crowned molars in many unrelated herbivorous mammals has been interpreted as an adaptation to eating hardy grasses.”
Other adaptations – like the abilities of animals like rhinos, giraffes and antelopes to run – were also fostered on the savannah.
Lehmann said: “Likewise, the locomotion and limbs of large African ungulates are understood as an adaptation to rapid movement in open, forest-free habitats such as the savannas.”
The study was published in the peer-reviewed academic journal ‘Science’ on Thursday, 13th April.
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