The evolutionary process of the first land-dwelling animals was surprisingly slowed for millions of years, as indicated by a study based on a monster ancestor species of all living beings.
According to SciTech Daily, a research team from the University of Bristol, University College London, and Pompeu Fabra University examined the skull fossils of 100 living and fossilized animal species, including 400 million-year-old four-legged fish.
Four-legged fish – resembling bizarre creatures that are part aquatic monster and part reptile – were the pioneering class that transitioned habitats from ocean to land, serving as ancestors to all land-dwelling animal lineages, from amphibians to humans.
Portrait of the “monster ancestor” tetrapod – (Photo: Mark Garlick)
However, there was a period during which these ancestors evolved quite slowly. The surprising reason for the “slowdown” of life on Earth has been revealed in a recently published paper in Science Advances: the skull.
According to lead author James Rawson from the School of Earth Sciences at the University of Bristol, the tetrapod skull, a representative of the four-legged fish group, has fewer skull bones than its ancestral species and fewer than later species.
This may sound counterintuitive, but having fewer skull bones actually made the skull structurally more complex. With fewer bones, each one had to connect with more neighboring bones, creating a complex and rigid structure that caused the organisms to become “stuck,” delaying the evolutionary process for millions of years.
It appears that the bizarre appearance of this rigid skull is related to an event that occurred 10 million years ago, which led to a decline in animal limbs.
Fortunately, this bottleneck has been gradually overcome by the miraculous process of evolution, allowing life on Earth to continue evolving robustly and diversely once again – a process closely linked to the emergence and evolutionary levels of all species, including humans today.
