All posts tagged: evolutionary biology

Which came first, the chicken or the egg? Evolution has a surprisingly clear answer

Which came first, the chicken or the egg? Evolution has a surprisingly clear answer

Published by Jenni Sidey

From an evolutionary perspective, eggs existed hundreds of millions of years before chickens, appearing in animal lineages long before birds evolved. The idea of a single “first chicken” is misleading because species emerge gradually as genetic differences accumulate across populations and generations. If the question specifically means the first egg containing an animal we would classify as a chicken, that egg would have been produced by parents that were almost, but not quite, modern chickens. The question sounds like an impossible loop. Chickens hatch from eggs, but chicken eggs come from chickens, leaving no obvious place for the cycle to begin. Evolutionary biology breaks that loop by changing the timescale. Egg-laying animals existed vastly earlier than chickens, and even bird-like eggs appeared long before anything resembling a domesticated chicken walked the Earth. That makes the broad scientific answer straightforward: the egg came first. The more interesting question is what counts as a “chicken egg” and whether evolution ever produced a single identifiable first chicken. Those questions lead from dinosaurs and ancient reproduction to genetics, domestication …

The law of kissing has changed dramatically across 4,500 years

The law of kissing has changed dramatically across 4,500 years

Published by Jenni Sidey

A kiss has served as affection, greeting, ritual, agreement and legal offense, with its meaning changing dramatically across cultures and historical periods. Romantic mouth-to-mouth kissing is not universal, and legal systems have likewise differed in deciding when kissing is protected, regulated or punished. Modern legal thinking has increasingly shifted away from family honor and public morality toward bodily autonomy and consent. A kiss can mark affection, seal an agreement, signal status or cross a legal boundary. Across centuries, legal systems have treated the same physical act as property, contract, ritual, moral offense and assault. That range is the subject of an analysis by Andrew Torrance, a University of Kansas law professor. Torrance examines what he calls “osculation regulation,” combining legal history with research from anthropology, psychology and evolutionary biology. His central point is that kissing has never carried one universal meaning. Romantic mouth-to-mouth kissing itself is not practiced everywhere, and the law has changed along with cultural ideas about intimacy, hierarchy and bodily autonomy. Auguste Rodin’s “The Kiss” is one of the most memorable depictions …

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 …

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 …

A single gene may explain why some males live fast and die young

A single gene may explain why some males live fast and die young

Published by Jenni Sidey

A small fish that lives fast and dies young has given biologists a rare look at one of evolution’s oldest bargains. In the African turquoise killifish, researchers traced that bargain to a single gene called vgll3, which helped push males toward faster growth and earlier sexual maturity. But the same shift also came with a darker side: shorter lives, more age-related tumors, and a higher risk of melanoma-like cancers in old age. The finding offers unusually direct evidence for antagonistic pleiotropy, a long-debated theory of aging that holds that some genes are favored because they improve early-life success, even if they cause damage later on. “We have effectively caught evolution in the act of making a trade-off,” said Dr. Itamar Harel of Hebrew University. “For years, we’ve asked why our bodies can’t just maintain themselves indefinitely. This gene gives us a direct answer: nature doesn’t prioritize longevity; it prioritizes continuity. We are built to sprint, not to marathon.” The killifish is an emerging model for investigating the genetic architecture of aging and age-related pathologies, which …

Scientists identify hundreds of ancient genes associated with human diseases

Scientists identify hundreds of ancient genes associated with human diseases

Published by Jenni Sidey

When a child develops kidney failure or a rare bone disorder, the cause can seem painfully immediate. It may be a single broken gene, a sudden diagnosis, or a family searching for answers. However, some of those faults may trace back nearly two billion years, to a one-celled ancestor shared by every plant, animal, and fungus alive today. A University of Texas at Austin-led team has now reconstructed the most detailed map yet of the protein networks inside that ancestor, known as the last eukaryotic common ancestor, or LECA. In doing so, the researchers built a new way to hunt for disease genes in humans. They used some of the oldest molecular machinery in complex life as a guide. Their study, published in Cell Genomics, suggests that the deep history of life is not just a story about origins. It can also help explain why modern bodies fail. Rachael Cox, a former UT doctoral student who led the data analysis in the lab of senior author Edward Marcotte, said the approach proved unexpectedly powerful. “There …

New AI model reconstructs human ancestry from DNA

New AI model reconstructs human ancestry from DNA

Published by Jenni Sidey

A stretch of DNA can look static on a screen, just long rows of A, T, C and G. But buried in those letters are small changes that mark where lineages split, rejoined and drifted over time. Researchers at the University of Oregon say they have built an artificial intelligence system that can read those mutation patterns much the way a language model reads text, then use them to estimate when two genes last shared a common ancestor. The tool, called cxt, is described in the Proceedings of the National Academy of Sciences and is aimed at one of population genetics’ hardest jobs: reconstructing the hidden family history inside a genome. Instead of predicting the next word in a sentence, the model predicts what the team calls the next coalescence, an estimate of shared ancestry along a chromosome. Andrew Kern, a computational biologist in the University of Oregon College of Arts and Sciences, said the work draws on ideas behind generative AI but puts them to use in a field that has largely relied on …

Evolution has used the same genetic ‘cheat sheet’ for over 120 million years

Evolution has used the same genetic ‘cheat sheet’ for over 120 million years

Published by Jenni Sidey

A yellow band across a wing might look like a simple flourish. In the South American rainforest, it can mean survival. Across butterflies and a day-flying moth that split from one another tens of millions of years ago, researchers found that near-identical warning patterns keep arising through the same small set of genes. The result points to something that has long intrigued evolutionary biologists: maybe evolution is not always as open-ended as it seems. The international team, led by scientists at the University of York and the Wellcome Sanger Institute, examined several distantly related species that belong to the neotropical tiger mimicry ring. These insects share bold wing patterns that warn birds and other predators to stay away. Because the species are toxic or distasteful, looking alike helps them all. If a bird has already learned that a certain pattern means bad news, any species wearing the same signal gains an advantage. What stood out in the analysis was not just that the wing patterns converged, but that the underlying genetics did too. Geographic distributions …

Caterpillars use precise vibrational patterns to communicate with ants

Caterpillars use precise vibrational patterns to communicate with ants

Published by Jenni Sidey

If you were small enough to fit inside an ant nest, you would hear it as much as you would see it. The walls shiver with tiny footsteps. The ground carries constant vibration. In that crowded, dark space, a caterpillar trying to survive has a problem: how do you convince a suspicious ant colony that you belong? A team led by researchers at the University of Warwick says some butterfly caterpillars may solve that problem with rhythm. The new work, conducted with the University of Turin and the Forest Research Institute and published in Annals of the New York Academy of Sciences, reports that caterpillars closely tied to ants produce precisely timed vibrational patterns that resemble the ants’ own signals. Chemical mimicry has long been known in these partnerships. This study argues that timing, down to steady beats and alternating long-short patterns, also helps caterpillars get treated like insiders. Dr. Chiara De Gregorio, a research fellow in Warwick’s Department of Psychology, put it bluntly: “These caterpillars are essentially speaking the ants’ language, not just chemically, …

The odd ways mammals descend trees and what it means for primate evolution

The odd ways mammals descend trees and what it means for primate evolution

Published by Jenni Sidey

A monkey descending a tree trunk often keeps its head up, moving almost like a cautious climber backing down a ladder. Squirrels and many other mammals, by contrast, tend to go headfirst. That difference turns out to carry clues about how primates evolved their distinctive upright postures. A new comparative analysis of tree-dwelling mammals, published in eLife, examined how animals move down vertical supports such as trunks and vines. The research compared 21 arboreal species, from primates to rodents and marsupials, making it the first broad study to analyze both upward and downward climbing across many mammal groups. The results point to a pattern shaped not just by body size, but by evolutionary history and anatomy. “While not all arboreal mammals traverse narrow terminal branches, they all rely on vertical supports to reach tree canopies,” said lead author Séverine Toussaint of the Center for Research on Paleontology in Paris. “Their ability to safely descend sloping and vertical supports remains important, yet largely understudied.” Two species from the study – a raccoon (Procyon lotor) and mongoose …