Taxonomy term

evolutionary biology

Predators may have spurred evolution of ancient brittle stars

Threats to species can encourage evolution, leading to animals with harder shells or other defensive adaptations. In a recent study in the Journal of Systematic Palaeontology, researchers found that while some ancient brittle stars — relatives of starfish with long, whip-like arms — evolved in the face of threats, some adapted a different approach: they moved.

10 Jan 2018

Horses evolved to get along: Competition between species not main evolutionary driver

Horses have changed size and shape dramatically over the last 20 million years, evolving from small dog-sized creatures with multiple toes into the large, hoofed grazing animals we see today. But the factors that drove these changes have been unclear. In a new study in Science, scientists tested the long-held theory that horses evolved rapidly to compete with one another during the worldwide expansion of grasslands starting 18 million years ago.

07 Jun 2017

Tiny fish illuminates tooth fairy mystery

When kids lose their milk teeth, the roots shrivel up and just the outer enamel falls out — a process known as basal resorption. Now, the discovery of a tiny jawbone from a 424-million-year-old fossil fish is shedding light on the origin of our modern mode of tooth replacement.

08 Mar 2017

Turtle shells evolved for burrowing, not protection

How the turtle got its shell is one of the long-standing conundrums of paleontology. Paleontologists know that one of the first steps toward a shell was a broadening of the ribs, which occurred about 50 million years before full shells evolved. But why the broadening, which conferred some disadvantages to movement and breathing, began, has been a mystery. Now, the discovery of a proto-turtle with a partial shell in South Africa is shedding some light on the early stages of shell development.

11 Nov 2016

Cretaceous amber suggests societal behavior in insects is at least 100 million years old

Many insects are social animals. Some, including ants, form colonies with complex social hierarchies, wherein specific roles like reproduction and colony construction are assigned to specific groups of ants, like queens or workers, for example. This kind of sociality, known as eusociality, is found in many other insects, like beetles, honeybees and termites. When it evolved, however, has remained unclear. Until now, the earliest evidence of eusociality came from 20-million-year-old fossils, even though the insect lineages were known to be much older. But two new fossil discoveries have pushed the first known appearance of eusociality back by 80 million years.

04 Jul 2016

Fish evolved quickly after earthquake

Evolution is often thought of as occurring over very long timescales, but as a tiny Alaskan fish demonstrates, significant changes can take place in just a few generations.

03 May 2016

Tree of life reshaped

Since the 1970s, the classic “tree of life” taught in classrooms has portrayed three domains of life — Archaea, Bacteria and Eukaryota — all descending from an unknown common ancestor. But behind the scenes, this textbook picture has been shifting. Many scientists now think the tree’s deepest root lies within the bacteria; and, even more recently, some have begun suspecting that the Eukaryota — including all animals, plants, fungi, slime molds and other organisms whose cells have nuclei — are actually an offshoot from the Archaea, paring the tree from three to two domains. Now, a new study furthers that claim, and with the help of a novel technique for parsing phylogenetic data in greater detail than ever before, suggests a revised backstory for the Archaea — and, by extension, us.
21 Oct 2015

A Cambrian-like explosion of mammals in the Mid-Jurassic

Dinosaurs dominated the continents during the Mesozoic, and for a long time, paleontologists assumed our mammalian ancestors kept a low-profile in that era, existing only as small, ground-dwelling, nocturnal insect-eaters. But in the last decade, discoveries of an ever-increasing diversity of mammal fossils have forced a rethink: Mesozoic mammals were also gliders, climbers, diggers and swimmers. Now, scientists looking at mammalian rates of evolution during the time of the dinosaurs have found that this diversity peaked in the Mid-Jurassic, leading to new physical characteristics that would remain for millions of years.
20 Oct 2015

Bigger is better in the sea

Since first appearing in the fossil record more than 550 million years ago, complex animals have steadily grown in average size, from millimeters to meters to many meters in length. This tendency of species to evolve toward larger sizes over time — known as Cope’s rule — has been studied before in individual species, such as horses and clams, but a new dataset of thousands of marine animals is giving scientists their first large-scale look at how Cope’s rule applies to whole ecosystems over hundreds of millions of years.
28 Jun 2015

Bird genomes untangle branches of avian family tree

Birds, the only surviving descendants of dinosaurs, have one of the most fascinating — and perplexing — family trees in the animal kingdom. To sort it out, an international collaboration known as the Avian Phylogenomics Project has sequenced the genomes of dozens of different bird species, representing all the orders in the bird family. Even with a glut of new data, however, many questions remain about the branches of the avian family tree.

22 Apr 2015