One of the most fascinating questions in biology is how major evolutionary transitions occur. How did animals evolve from single-celled organisms? How did birds evolve from dinosaurs? How did mammals evolve from reptiles?
These are some of the examples of dramatic changes in the history of life that have puzzled scientists for centuries.
A new study by researchers at the University of Sheffield sheds light on this question by examining a group of marine snails that have undergone a remarkable transition in their reproductive mode.
The study reveals how this transition happened gradually rather than in a single leap, and how it involved many small genetic changes that accumulated over time.
The study, published in the journal Nature Ecology and Evolution, has important implications for understanding the evolutionary processes that shape the diversity of life on Earth. It also challenges some of the popular misconceptions about how evolution works and how it leads to new functions.
Unlocking Evolution's Mysteries: The Marine Snails Revelation
By studying the whole-genome sequences of a group of marine snails, they have gained insights into the gradual nature of significant evolutionary changes.
These marine snails, common on the rocky shores of Europe, the U.K., and the East Coast of the U.S., have become central to understanding how game-changing innovations like flight, vision, and live-bearing offspring evolved.
Contrary to popular belief in dramatic "monster" steps or "hopeful monsters," evolution appears to be a series of small, incremental steps occasionally leading to striking new functions.
The study reveals that these marine snails have recently transitioned from egg-laying to live birth. This shift is seen as an intermediate stage in evolution-a living proof against the notion that such significant transitions occur suddenly.
This revelation underscores natural selection's role in favoring gradual mutations over large-effect mutations. It provides tangible evidence against theories suggesting abrupt changes and supports a more nuanced understanding of evolutionary processes.
According to the lead author of the study, Dr. Tim Carvajal, the findings challenge the idea that major evolutionary transitions happen in one big leap.
Dr. Carvajal that they show that they are the result of many small changes accumulating over time and occasionally leading to new functions.
He also said that this is important because it helps people appreciate the complexity and diversity of life on Earth and how it came to be.
He added that it also has implications for how people approach conservation and management of biodiversity in the face of environmental change.
The study, published in the journal Nature Ecology and Evolution, involved analyzing the genomes of 18 species of Littorina snails, which vary widely in their reproductive modes, shell shapes, and habitats.
The researchers found that the snails share a common ancestor that lived about 20 million years ago and that their differences emerged gradually through natural selection.
The researchers also identified genes that are associated with the transition from egg-laying to live birth, such as those involved in maternal-fetal interactions, nutrient transport, and immune response.
They found that these genes have been evolving rapidly in the live-bearing snails, suggesting that they are under strong selection pressure.
The study is part of a larger project funded by the European Research Council, which aims to understand the genetic and ecological factors that drive the evolution of reproductive modes in animals.
Dr. Carvajal said that he hopes that the study will inspire more research on the molecular mechanisms and evolutionary dynamics of major evolutionary transitions, which are still poorly understood.
He also said that he hopes that it will raise awareness of the importance of preserving the diversity of life on Earth, which is the result of millions of years of evolution.
