Evolution's recipe book: How 'copy paste' errors led to insect flight, octopus camouflage and human cognition
Seven hundred million years ago, a remarkable creature emerged for the first time. Though it may not have been much to look at by today's standards, the animal had a front and a back, a top and a bottom. This was a groundbreaking adaptation at the time, and one which laid down the basic body plan which most complex animals, including humans, would eventually inherit.
The inconspicuous animal resided in the ancient seas of Earth, likely crawling along the seafloor. This was the last common ancestor of bilaterians, a vast supergroup of animals including vertebrates (fish, amphibians, reptiles, birds, and mammals), and invertebrates (insects, arthropods, mollusks, worms, echinoderms and many more).
To this day, more than 7,000 groups of genes can be traced back to the last common ancestor of bilaterians, according to a study of 20 different bilaterian species including humans, sharks, mayflies, centipedes and octopuses. The findings were made by researchers at the Centre for Genomic Regulation (CRG) in Barcelona and are published today in the journal Nature Ecology & Evolution.
Remarkably, the study found that around half of these ancestral genes have since been repurposed by animals for use in specific parts of the body, particularly in the brain and reproductive tissues. The findings are surprising because ancient, conserved genes usually have fundamental, important jobs that are needed in many parts of the body.
When the researchers took a closer look, they found a series of serendipitous "copy paste" errors during bilaterian evolution were to blame. For example, there was a significant moment early in the history of vertebrates. A bunch of tissue-specific genes first appeared coinciding with two whole genome duplication events.
Animals could keep one copy for fundamental functions, while the second copy could be used as raw material for evolutionary innovation. Events like these, at varying degrees of scale, occurred constantly throughout the bilaterian evolutionary tree.
"Our genes are like a vast library of recipes that can be cooked up differently to create or change tissues and organs. Imagine you end up with two copies of a recipe for paella by accident. You can keep and enjoy the original recipe while evolution tweaks the extra copy so that it makes risotto instead.
"Now imagine the entire recipe book is copied—twice—and the possibilities it opens for evolution. The legacy of these events, which took place hundreds of millions of years ago, lives on in most complex animals today," explains Federica Mantica, author of the paper and researcher at the Centre for Genomic Regulation (CRG) in Barcelona.
The authors of the study found many examples of new, tissue-specific functions made possible by the specialization of these ancestral genes. For example, the TESMIN and tomb genes, which originated from the same ancestor, ended up independently playing a specialized role in the testis both in vertebrates and insects. Their importance is highlighted by the fact that problems with these genes can disrupt sperm production, affecting fertility in both mice and fruit flies.
The specialization of ancestral genes also laid some foundations for the development of complex nervous systems. For example, in vertebrates, the researchers found genes critical for the formation of myelin sheaths around nerve cells, which are essential for fast nerve signal transmission. In humans they also identified FGF17, which is thought to play an important role in maintaining cognitive functions into old age.
In insects, specific genes became specialized in muscles and in the epidermis for cuticle formation, contributing to their ability to fly. In the skin of octopuses, other genes became specialized to perceive light stimuli, contributing to their ability to change color, camouflage and communicate with other octopuses.
By studying the evolution of species at the tissue level, the study demonstrates that changes in the way genes are used in different parts of the body have played a big role in creating new and unique features in animals. In other words, when genes start acting in specific tissues, it can lead to the development of new physical traits or abilities, which ultimately contributes to animal evolution.
"Our work makes us rethink the roles and functions that genes play. It shows us that genes that are crucial for survival and have been preserved through millions of years can also very easily acquire new functions in evolution.
"It reflects evolution's balancing act between preserving vital roles and exploring new paths," concludes ICREA Research Professor Manuel Irimia, co-author of the paper and researcher at the Centre for Genomic Regulation.
More information: Evolution of tissue-specific expression of ancestral genes across vertebrates and insects, Nature Ecology & Evolution (2024). DOI: 10.1038/s41559-024-02398-5
Journal information: Nature Ecology & Evolution
Provided by Center for Genomic Regulation
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The evolving attitudes of Gen X toward evolution
As the centennial of the Scopes Monkey Trial of 1925 approaches, a new study illustrates that the attitudes of Americans in Generation X toward evolution shifted as they aged.
The study, led by Jon D. Miller, research scientist emeritus in the Institute for Social Research at the University of Michigan, found that while students in middle and high school tended to express uncertain attitudes toward evolution, those attitudes solidified as they graduated high school, went to college and entered the workforce.
"Some may challenge whether the evolution issue is still of relevance and consider it to be a harmless curiosity," Miller said. "U.S. science and technology continue to prosper, although a substantial minority of American adults reject the idea that humans developed from earlier species of animals.
"However, we believe that there are numerous examples of public policy over recent decades when an understanding of basic biological constructs would have helped inform public and political debate on those issues."
The study, published in the journal Public Understanding of Science, used data collected from about 5,000 participants born in the center of Generation X, 1971-1974, over the course of 33 years, from middle school to midlife.
"Research on attitudes toward science typically uses a single survey or a series of surveys of different participants," Miller said. "Using the three-decade record from the Longitudinal Study of American Life enables our study to investigate how attitudes develop and shift over formative decades in the same individuals."
Middle school and high school students displayed a good deal of uncertainty about evolution, with a third having no attitude about evolution and 44% saying that the statement "human beings as we know them developed from earlier species of animals" was probably true or probably false, reflecting a degree of uncertainty about the issue.
During the 15 years after high school, 28% of these Generation X young adults concluded that evolution was definitely true and 27% thought that evolution was definitely false, according to co-author Mark Ackerman, a professor at Michigan Engineering, the U-M School of Information and Michigan Medicine.
"These results demonstrate the impact of postsecondary education, initial career experiences and the polarization of the political system in the United States," Ackerman said.
During the next 15 years (from their early 30s to their late 40s), these Generation X LSAL participants reported a small increase in the proportion of individuals seeing evolution as definitely true (30% in 2020) and a small decrease in the proportion seeing evolution as definitely false (23% in 2020). These results reflect the stabilization of the lives of LSAL respondents, with substantial numbers entering a career of their choice, starting a family and becoming more engaged with their community.
The study investigated the factors that were associated with the participants' attitudes toward evolution at three points during the study. As in a previous study by the same researchers, factors involving education tended to be strong predictors of the acceptance of evolution, while factors involving fundamentalist religious beliefs tended to be strong predictors of the rejection of evolution.
The experience of college-level science courses, the completion of baccalaureate or more advanced degrees, and the development of civic scientific literacy were strong predictors of increased acceptance of evolution.
"Our analysis of a unique longitudinal dataset allowed us to explore the development of attitudes toward a scientific topic in unprecedented detail," Miller said. "And understanding the public's attitudes toward evolution is of particular importance, since evolution is going to continue to be central to biological literacy and—scientific literacy—in the 21st century."
Besides Miller and Ackerman of the University of Michigan, authors included Belén Laspra and Carmelo Polino of the University of Oviedo (Spain), Glenn Branch of the National Center for Science Education, and Robert Pennock of Michigan State University.
Study: The acceptance of evolution: A developmental view of Generation X in the United States (DOI: 10.1177/09636625241234815)
JOURNAL
Public Understanding of Science
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