Ancient teeth suggest humans were using psychoactive betel nuts 25,000 years ago, pushing the history of habitual drug use deep into the Ice Age. Archaeologists from Griffith University have found evidence suggesting that humans were using mind-altering substances far earlier than previously believed. The research team, led by Professor Adam Brumm of Griffith’s Australian Research [...]Horseshoe crabs are marine animals more closely related to spiders than crabs. These animals have existed for more than 450 million years, and are sometimes called “living fossils” because they appear to have changed very little throughout their evolutionary history. However, horseshoe crabs have a poor fossil record, so this apparent lack of change could also be due to a lack of evidence, particularly when it comes to their reproduction. Scientists want to know: Are horseshoe crabs truly living fossils?
Modern horseshoe crabs reproduce by releasing hundreds of eggs and sperm into tidal waters, via a process called external fertilization. Until now, scientists have assumed that horseshoe crabs have always reproduced this way. But paleontologists have only found 3 fossil horseshoe crabs from the past 252 million years with their reproductive systems preserved, so this assumption is mainly based on an absence of evidence to the contrary.
Scientists in the past interpreted the horseshoe crab’s long history of external fertilization as indicative of its evolutionary consistency. However, James Lamsdell and colleagues recently discovered a new fossil species of horseshoe crab in the 450 million-year-old Big Hill Formation in Michigan that challenges this assumption.
To study the specimen, the scientists photographed it under 2 types of microscopes. The first type of microscope used polarized light to see structures in the fossil that may have blended into the rock, like putting on special glasses to see subtle textures. The second type of microscope used fluorescent light to reveal soft tissue in the fossil. Only some tissues, like ovarian tissue and preserved eggs, glow under fluorescence, so this method helped the team rule out non-biological structures, like bubbles, cracks, or minerals.
The researchers found that their analytical techniques revealed remarkable details about the ancient horseshoe crab. One unique feature of the fossil was the shape of its exoskeleton. The fossil’s exoskeleton had a more shovel-like appearance than that of modern horseshoe crabs, which are less elongated and more round. It was also about 11 times smaller than a modern adult horseshoe crab.
The researchers also discovered that the fossil preserved an intricate network of ovaries containing unfertilized eggs. This ovarian network lined the interior surface of the shell in a band of interconnected tubes, preserving both unfertilized eggs and developing eggs. They noted that the fossil eggs were all about 0.1 to 0.15 millimeters in diameter, about the same width as a human hair. This size consistency suggested that all the eggs developed at the same time, via a process called synchronous development.
Since the fossil crab’s ovarian tubes contained developing eggs, it was an adult, meaning that the earliest adult horseshoe crabs were significantly smaller and shaped differently than modern adult horseshoe crabs. Despite their differences in size and shape, the fossil horseshoe crab’s reproductive system closely mirrored its modern one, in terms of its ovarian system and synchronous development of eggs. As in previous studies, it showed no evidence of internal fertilization.
The researchers concluded that the earliest horseshoe crabs also reproduced through external fertilization. This fossil horseshoe crab is more than 215 million years older than preexisting fossils preserving evidence of external fertilization, and suggests that the horseshoe crab’s mode of reproduction has been conserved for almost half a billion years!
However, the team’s findings reveal a more nuanced evolutionary history for the horseshoe crab than previously assumed. Although they’ve maintained the same reproductive system for almost half a billion years, the size and shape of their exoskeleton have changed. This discovery reveals that different parts of the horseshoe crab evolved at different rates. It seems that horseshoe crabs are not entirely the living fossils scientists once thought… while their bodies have evolved, their reproduction has endured.
The post Are horseshoe crabs truly “living fossils”? appeared first on Sciworthy.
Ancient animal waste may have helped fuel the development and diversification of early marine ecosystems. Tiny pellets of fossilized waste may preserve evidence of a major transformation in early animal life. An international study led by Flinders University proposes that excrement helped reshape ancient oceans during one of evolution’s most important turning points. The researchers [...]ASU researchers found that genetics alone cannot explain the origins of eusociality. Inside an ant colony, queens reproduce while workers care for young and maintain a society built around shared labor. For more than six decades, evolutionary biologists have debated whether this extraordinary arrangement, known as eusociality, arose partly because ants, bees, and wasps share [...]A leaf-eared mouse living more than 6,700 meters (22,000 feet) above sea level in the Andes has shattered assumptions about where mammals can survive. Near the summit of an Andean volcano, where the air contains barely half as much oxygen as it does at sea level, scientists found something that should not have been there: [...]Koalas survived a climate-driven population crash 100,000 years ago, and new genomic research is helping scientists better protect the species today. A major genomic study has transformed scientists’ understanding of koala (Phascolarctos cinereus) evolution, showing that the species underwent a dramatic population decline about 100,000 years ago, long before humans reached Australia. Researchers found that [...]
A century after one of developmental biology’s most influential experiments, researchers have revisited the concept of the embryonic “organizer” in one of the oldest animal lineages alive today. A tiny cluster of cells in an embryo can act like a construction manager for an entire body. It helps determine which end becomes the head, which [...]Harvard researchers found that adding a little randomness to robot movements can prevent gridlock and dramatically boost efficiency in crowded swarms. Imagine a swarm of robots sent into a tight space to handle an urgent job, such as cleaning up an oil spill or assembling complex equipment. At first, adding more robots speeds things up. [...]Remote Scottish islands turned tiny wrens into giant birds that may be evolving into new species. Tiny wrens living on remote Scottish islands are providing scientists with a rare look at how evolution can reshape animals in isolated environments. A new study led by researchers at the University of Birmingham found that several island populations [...]
An analysis of dental tartar containing traces of human diets dating back over 33,000 years has revealed that ancient Europeans and many early Asian populations likely only ate insects by accident, perhaps as larvae in the carcasses of dead animals.
Conversely, the new study found that intentional insect consumption, called entomophagy, was more common in tropical regions and among Neanderthal populations.
Although the difference has some cultural and religious roots, the team found evidence that the abundance of insects in the tropics and the decreasing ability of humans migrating away from the tropics to digest insects likely led to the modern-day separation over thousands of years.
The Institute of Evolutionary Biology (IBE), a joint center of the Spanish National Research Council (CSIC) and Pompeu Fabra University (UPF), research team behind the new findings suggests their research could help explain why some modern populations still consume insects as food while other parts of the world consider it gross or taboo, especially given the increasing food demands of a rising world population.
According to a statement announcing the new research, hundreds of millions of people currently include insects in their diet. However, they also note that most of the Western world continues to “show an aversion” to including any of the more than 1,611 insect species designated as edible by the Food and Agriculture Organization of the United Nations (FAO) in theirs. Although some theories suggest the difference is almost purely cultural, the team concedes that “its origin remains unknown.”
To explore the origins of human entomophagy, the IBE analyzed 745 samples of ancient human dental tartar dating back to 33,000 before present. According to the team’s results published in the journal Science Advances, dental tartar (sometimes called dental ‘calculus’) is a critical archaeological tool because it preserves the DNA of the species these human ancestors consumed during their lifetimes.
Although the analysis found evidence for entomophagy amongst virtually all ancient populations sampled in the study, the levels varied dramatically. Notably, the evidence suggested that ancient humans in northern Eurasia did not routinely eat insects in measurable quantities. Instead, any consumption was likely incidental, including consumption of insect larvae in rotting food.
Curious whether the lack of entomophagy in ancient European and Central and Northern Asian populations was purely cultural or whether genetic and geographic factors were involved, the team studied human genes involved in chitin digestion. Chitin, which can be found in some marine animal shells, is also part of an insect’s hard exoskeleton.
According to the study authors, the analysis revealed that the ‘chitinase’ genes in North Eurasian human populations “carry mutations that confer a reduced capacity to digest insect exoskeletons.” Their analysis revealed that this reduced capacity to digest insect exoskeletons has persisted in the genomes of modern Eurasian populations “for the last 9,000 years,” which would coincide with the widely accepted date for the origin of agriculture.
Pablo Librado, study leader and a principal investigator at the IBE, said the “scarce presence of insects in the diet of northern Eurasians” suggests that the cause may not lie solely in more recent cultural factors but also in ecological and evolutionary components dating back several millennia.
When the team compared data from ancient human tartar with that of ancient Neanderthals, they found that Neanderthals engaged in much higher levels of entomophagy than humans living in the same regions. According to the study authors, Neanderthal insect consumption levels were similar to those found in western chimpanzee populations, which the researchers note “rely on entomophagy to supplement their diet on the savanna, especially during periods of drought.”
Further analysis of the extracted insect DNA showed that the group most commonly consumed by the Neanderthal specimens included flies and mosquitoes. Although the team only analyzed the DNA, they noted that a recent hypothesis suggests Neanderthals ate carcasses laden with mosquito larvae.
“The abundance of mosquito remains reinforces the possibility that the carcasses of their prey were kept in ponds and marshy areas, where mosquitoes lay their eggs,” the team’s statement explained.
An analysis of the Neanderthal DNA and the DNA from the lone Denisovan study subject revealed that both ancient hominid populations could digest chitin. This result reinforced the genetic basis for increased or reduced entomophagy beyond cultural factors.
One geographic component identified by the chitinase DNA analysis showed higher levels of digestive enzyme expression among humans living in or near the tropics. However, the expression of these enzymes gradually decreased as populations moved away from tropical regions. The team said this variation, which has been maintained for at least the last 9,000 years, “reflects the abandonment of entomophagy in European populations.”
Manuel Piñero, a predoctoral researcher at the IBE and first author of the study, noted that large numbers of insects must be consumed to offset the “high caloric cost” of collecting them, which might explain the higher levels of entomophagy in this region.
“In the tropics, there is a greater availability of social insects, such as termites and locusts,” Piñero explained, adding that the biomass and diversity of tropical edible insects enable “sustainable exploitation throughout the year.” The researcher also noted that insect consumption “adds to pest control.”
When discussing the implications of their findings, Librado highlighted the DNA and geographic factors the IBE team uncovered.
“Beyond cultural or religious factors, our results suggest that the reduced availability of insects in non-tropical areas may have been a key factor in the abandonment of entomophagy, leading to a reduced capacity to digest insect exoskeletons,” the researcher explained.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.
New DNA evidence reveals bed bugs tracked human expansion from ancient caves to modern cities.A new evolutionary analysis suggests the behavior appears across many bird groupsThe loss of a queen triggers intense battles for power among female wasps, disrupting the colony’s social structure. Surprisingly, other wasps avoid the fighting and keep the colony functioning by taking care of its most important daily tasks. What happens when a queen suddenly disappears from a wasp colony? According to new research led by [...]Leishmania parasites appear to evolve through widespread genetic exchange, reshaping assumptions about how they adapt and spread. A parasite long thought to spread mostly by cloning itself may be far more genetically dynamic than scientists once believed. A new international study suggests that Leishmania—a group of microscopic parasites responsible for debilitating tropical diseases—regularly swaps genetic [...]A newly described fossil goose shows that New Zealand’s bird history involved repeated arrivals, extinctions, and rapid island evolution. A rare fossil goose found in the remains of an ancient lake in Central Otago is changing how scientists understand the bird history of Aotearoa New Zealand, according to a researcher at the University of Otago [...]
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