[ad_1]
A study has found that the key to how vertebrates emerged from the ocean and began to conquer land some 390 million years ago may lie in the bone of the arm.
Experts from the United States and the UK have found that the development of the humerus – the bone that runs from the shoulder to the elbow – makes animals better walkers than swimmers.
This development led to the emergence of tetrapods – four-legged animals that, unlike their aquatic ancestors – lived primarily on land.
This triggered the emergence of tetrapods – four-legged animals that mostly live on land. Their ancestors had been confined to water.
This discovery sheds light on a key process in the history of evolution – the transformation of fins into limbs – that has been poorly understood.
Experts from the United States and the United Kingdom have found that the development of the humerus – the bone that runs from the shoulder to the elbow – makes animals better walkers than swimmers. This led to the emergence of tetrapods (pictured) – four-legged animals that, unlike their aquatic ancestors – lived primarily on land.
“Being able to walk on earth has essentially paved the way for all biodiversity and established modern terrestrial ecosystems,” said author and zoologist Stephanie Pierce of Harvard University.
“This represents an incredibly important period of time in the history of evolution.
Scientists have been trying to unravel the mysteries underlying vertebrates’ transition to earth for over a century.
The first tetrapods like Acanthostega and Ichthyostega were the first vertebrates to have limbs with fingers, instead of fish-like fins.
Their descendants include amphibians, reptiles, and extinct and living mammals – including us humans.
The humerus is invaluable for movement because it hosts key muscles that take up much of the stress generated by quadrupedal locomotion – that is, on all fours.
Additionally, bone is found in all tetrapods as well as the fish they evolved from – and is fairly common throughout the fossil record.
In view of this, the bone represents a kind of time capsule, as it can be examined throughout the fin-limb transition, the researchers explained.
“ We got into the idea that the humerus should be able to tell us about the functional evolution of locomotion as you go from being a swimming fish and come ashore and start walking, ” said author Blake Dickson.
In their study, the team analyzes 3D reconstructions of 40 fossilized humeras – including recently collected specimens, dating back more than 350 million years, found by researchers at the University of Cambridge.
The team ran their data through a supercomputer for thousands of hours – a span of almost four years – to assess how the bone likely changed over time and what impact that may have had on how the creatures were moving.
The analysis covered the transition from aquatic fish to terrestrial tetrapods – including an intermediate type with previously unknown locomotor abilities.
The researchers found that the emergence of members in the latter group coincided with the transition to the land – but that these pioneers were not good at walking.
They found that an early ‘L’ shaped humerus (middle) derived from lumpy fish bone (left) provided some advantage for moving around on land – but not much. Pioneer creatures had a long way to go before they developed the ability to use their limbs with ease. Later, the bone evolved into a more robust, elongated and twisted shape (right) – leading to more efficient gaits which helped fuel new biodiversity and expanding ecosystems
As these creatures left the water, their humerus bones changed shape, resulting in new functional traits that were found to be more beneficial for life on earth.
It makes sense, Dickson said. He added: ‘You can’t be good at everything. You have to give up something to go from being a fish to being a tetrapod on earth.
The team captured these changes on a morphological map showing how early tetrapods were compared to water or land dwellers.
They found that an early “L” shaped humerus provided some benefit for moving around on earth – but not much. Pioneer creatures had a long way to go before they developed the ability to use their limbs with ease.
The analysis covered the transition from aquatic fish (left) to terrestrial tetrapods (right) – including an intermediate type (middle) with previously unknown locomotor abilities. The researchers found that the emergence of members in the latter group coincided with the transition to the land – but that these pioneers were not good at walking.
Later, the bone evolved into a more robust, elongated and twisted shape – leading to more efficient gaits that helped fuel new biodiversity and expanding ecosystems.
This “ demonstrates the amount of information you can get from such a small part of an animal’s skeleton that has been recorded in the fossil record, ” Professor Pierce said.
Analyzing these elements, she added, has helped “unravel one of the greatest evolutionary transformations that has ever occurred. This is really cutting edge stuff.
The full results of the study were published in the journal Nature.
[ad_2]
Source link