Humanity Chopping Down Tree of Life, New Research Warns
By Jessica Corbett
Underscoring the urgent need for increased and intensely focused conservation efforts, new research shows that human activity worldwide is wiping out plant and animal life—including our own—so rapidly that evolution can't keep up.
Paleontologist and lead researcher Matt Davis of Denmark's Aarhus University warned, "We are starting to cut down the whole tree [of life], including the branch we are sitting on right now."
"We are doing something that will last millions of years beyond us," Davis told the Guardian. "It shows the severity of what we are in right now. We're entering what could be an extinction on the scale of what killed the dinosaurs."
The analysis, published Monday in the Proceedings of the National Academy of Sciences, specifically focused on mammals that currently exist as well as those which went extinct as humans spread across the globe, but it provides insight on the broader biodiversity crisis. It adds to a growing body of recent research that has warned of imminent mass extinction driven by unsustainable human activity, the climate crisis, and inadequate conservation efforts.
Even under the best circumstances, with dramatic improvements to current conservation work, the new analysis posited it will take 3-5 million years "just to diversify enough to regenerate the branches of the evolutionary tree that they are expected to lose over the next 50 years. In addition, the study found it could take 5-7 million years "to restore biodiversity to its level before modern humans evolved," according to a statement outlining the findings.
The degree of biodiversity loss over the next five decades will be significantly influenced by the changes to current human behaviors, or lack thereof—but the impact of losing species can vary greatly.
"Large mammals, or megafauna, such as giant sloths and saber-toothed tigers, which became extinct about 10,000 years ago, were highly evolutionarily distinct. Since they had few close relatives, their extinctions meant that entire branches of Earth's evolutionary tree were chopped off," Davis explained. Today, meanwhile, "there are hundreds of species of shrew, so they can weather a few extinctions."
While Davis said that "we have no reason to assume we will ever be able to bring extinction rates back down to normal background levels," he pointed out that the new research "highlights species we should try to save and could help us prioritize conservation."
"We once lived in a world of giants: giant beavers, giant armadillos, giant deer, etc., we now live in a world that is becoming increasingly impoverished of large wild mammalian species. The few remaining giants, such as rhinos and elephants, are in danger of being wiped out very rapidly," noted Jens-Christian Svenning from Aarhus University.
The team determined that species which could benefit from extra conservation efforts now—before it's too late to save them—include the black rhino, the red panda, and the indri. As Davis concluded, "It is much easier to save biodiversity now than to re-evolve it later."
Reposted with permission from our media associate Common Dreams.
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By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>
Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>
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