All posts tagged: fossil record

Ancient animal feces may have helped transform Earth’s oceans 540 million years ago

Ancient animal feces may have helped transform Earth’s oceans 540 million years ago

Published by Jenni Sidey

Fossilized feces suggest animal waste became an important source of nutrients as marine ecosystems grew more complex during the Cambrian Period. A review of Cambrian coprolites links the rise of digestive systems, new feeding strategies and nutrient recycling with the rapid diversification of animal life. Researchers argue that fecal matter did not cause the Cambrian Explosion by itself, but may have helped create conditions that supported richer food webs and new marine habitats. Ancient animal waste may have helped transform Earth’s oceans more than 500 million years ago. A new international study led by Flinders University argues that fossilized feces played a key role in one of evolution’s greatest turning points. The review describes what researchers call the “faecal revolution.” It links the rise of animal digestion, fecal pellets and nutrient recycling to the Cambrian Explosion about 540 million years ago. During that short and dramatic period, many major animal groups began to appear. Marine ecosystems became richer, more layered and more like the oceans you would recognize today. An Overlooked Force In Evolution Scientists …

Australopithecus findings could rewrite how we classify millions of years of human evolution

Australopithecus findings could rewrite how we classify millions of years of human evolution

Published by Jenni Sidey

The traditional labels Homo, Australopithecus and Paranthropus may no longer match the tangled relationships revealed by the human fossil record. A Monash University researcher proposes placing those groups, along with Kenyanthropus, inside a broader Homo genus stretching back about 4 to 5 million years. The change could make human classification more consistent and stable, but it would not settle every disputed relationship among ancient relatives. Human evolution may need a new name for much of its family tree. Fossils once separated into Homo, Australopithecus and Paranthropus increasingly resist those neat divisions, raising a basic question about whether the labels still match ancestry. A new analysis from Monash University argues that species assigned to those three groups, along with Kenyanthropus, should instead be placed within an expanded genus Homo. The proposal would stretch Homo back roughly 4 to 5 million years, far beyond its usual range. “Recent fossil discoveries and advances in evolutionary and genetic analysis make this an ideal time to reconsider whether our traditional taxonomy still accurately reflects human evolution,” Dr Towle said. Paranthropus …

Scientists discover why tiny dinosaurs never roamed the Earth

Scientists discover why tiny dinosaurs never roamed the Earth

Published by Jenni Sidey

The smallest known non-bird dinosaurs were far larger than the tiniest mammals, birds, and reptiles alive today. Energy-based models could not explain this size gap, suggesting competition and other ecological pressures constrained dinosaur evolution. Early birds may have escaped those limits through flight, opening new habitats where much smaller bodies became possible. A dinosaur could tower over a house, yet even the smallest known non-bird species never shrank to mouse size. That missing lower limit may reveal a forgotten evolutionary rivalry. An analysis in the journal Evolution suggests physiology alone cannot explain why non-avian dinosaurs stayed unusually large. Competition with small mammals may have blocked them from occupying the tiniest body-size ranges. “Everyone loves a giant dinosaur,” said Roger Benson, the Macaulay Curator of Dinosaur Paleobiology at the Museum. “But we decided to look at the other end of the scale. The absence of tiny dinosaurs may be just as interesting as the existence of giant ones. We already knew that dinosaurs prevented mammals from evolving to large sizes before the end-Cretaceous mass extinction. Here …

Tunas became large, warm-blooded predators long after the dinosaur extinction

Tunas became large, warm-blooded predators long after the dinosaur extinction

Published by Jenni Sidey

Tunas did not become large, fast and warm-blooded simply because an asteroid cleared the oceans of competing predators. Their defining traits appeared separately over tens of millions of years, complicating a familiar story about life after mass extinction. The asteroid impact 66 million years ago erased non-avian dinosaurs and many large marine predators. One long-held explanation proposed that tunas and other powerful fishes quickly expanded into the empty ecological roles. A new analysis from Yale University challenges that idea. By combining genetic evidence with fossils, researchers built the most complete time-calibrated evolutionary tree yet for Scombridae, the family that includes tunas, mackerels, bonitos and related fishes. The tree places the family’s origin near the Cretaceous-Paleogene extinction. Yet the traits that make modern tunas exceptional did not appear together or immediately afterward. Three independent origins of endothermy in Scombridae. Time-calibrated phylogeny of Scombridae estimated using a Bayesian node-dating approach, with branches coloured according to an ancestral state reconstruction of endothermy. (CREDIT: Proceedings of the Royal Society B) “Our results demonstrate the K-Pg extinction did not trigger …

Scientists finally confirm the cause of Earth’s greatest mass extinction

Scientists finally confirm the cause of Earth’s greatest mass extinction

Published by Jenni Sidey

Around 252 million years ago, Earth’s oceans became a lethal test of animal physiology. Nearly every marine species vanished, yet some groups survived well enough to dominate the seas ever since. The difference may have come down to how bodies handled heat and oxygen. The Permian–Triassic extinction, often called the Great Dying, eliminated about 96% of marine species and 70% of land animals. Its effects were not evenly spread across the evolutionary tree. Brachiopods, which resemble clams, nearly disappeared. Sea lilies, or crinoids, and other slow-moving seafloor animals also suffered enormous losses. These groups had dominated marine ecosystems for roughly the first 280 million years of animal life. Mollusks fared better. About half of clams, snails, and related groups survived. Their descendants, along with fish, starfish, and sea urchins, later became central players in modern oceans. Studying the metabolism of living brachiopods like these collected from San Juan Island, Washington, allowed Stanford researchers to understand how the physiology of the modern fauna and Paleozoic fauna may have differed and how these groups would have been …

Humans nearly went extinct 930,000 years ago, researchers find

Humans nearly went extinct 930,000 years ago, researchers find

Published by Jenni Sidey

For more than a century, human origins have been told as a story of expansion, migration, and survival. But deep in that story sits a long, quiet stretch when almost nothing seems to happen. Fossils thin out. The trail goes cold. Then our lineage reappears. A new genetic analysis argues that this silence was anything but uneventful. Between about 930,000 and 813,000 years ago, the ancestral population that eventually gave rise to modern humans appears to have fallen to an average of roughly 1,280 breeding individuals. According to a new study, published in the journal Science, that collapse lasted about 117,000 years. Moreover, it wiped out nearly 98.7 percent of the ancestral population at the start of the bottleneck. It also erased about 65.85 percent of the genetic diversity seen in the lineage before it. That number is startling on its own. It is even more striking when set against the fossil record. Human remains in Africa and Eurasia become unusually scarce between roughly 950,000 and 650,000 years ago during this interval. Schematic diagram of …