Evolutionary Biology on EARTH Magazine

Origins of plant photosynthesis illuminated

Tue, 10 Apr 2018 11:49:51 -0400

Bangiomorpha pubescens is a fossil red alga that's now the oldest-known direct ancestor of plants. Credit: Nicholas Butterfield.

Photosynthesis, the process by which plants harness sunlight to make their food, is a defining feature of plants and an important evolutionary development. But when photosynthesis evolved in ancient plant ancestors is not clear. The Precambrian fossil red alga Bangiomorpha pubescens, discovered in the Canadian Arctic in 1990 by University of Cambridge paleobiologist Nicholas Butterfield, displays evidence of traits that suggest it photosynthesized the way plants do, but the exact age of the fossil was also unknown. In a new study, researchers report an age for the alga of about 1.047 billion years, making it the oldest-known direct ancestor of plants.

Predators may have spurred evolution of ancient brittle stars

Thu, 14 Dec 2017 18:07:42 -0500

Fossils of roughly 275-million-year-old brittle stars were found in Western Australia. Credit: Kenneth McNamara.

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.

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

Wed, 17 May 2017 10:05:52 -0400

Artist's depiction of three species of Hipparion, which lived in the Iberian Peninsula between 9 million and 5 million years ago. Credit: Mauricio Anton.

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.

Tiny fish illuminates tooth fairy mystery

Thu, 16 Feb 2017 11:01:35 -0500

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.

Turtle shells evolved for burrowing, not protection

Tue, 18 Oct 2016 13:41:31 -0400

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.

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

Thu, 16 Jun 2016 12:46:14 -0400

Cretaceous-aged ants, thought to be fighting one another, preserved in amber. Credit: AMNH/D. Grimaldi and P. Barden.

Researchers recently identified previously unknown termites in fossilized amber samples. At left is the soldier caste of Gigantotermes rex, while at right are specimens of Krishnatermes yoddha from three castes: winged reproductive, worker and soldier. Credit: AMNH/D. Grimaldi.

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.

Fish evolved quickly after earthquake

Thu, 21 Apr 2016 16:10:05 -0400

A male three-spined stickleback. Credit: Mark Currey.

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.

Tree of life reshaped

Thu, 08 Oct 2015 10:38:03 -0400

Researchers considered several possible scenarios depicting the relationship between eukaryotes and two groups of archaea: the TACK group and Euryarchaeota. Three variations of scenario 1 all indicate a common, but unknown, root for all three groups, with eukaryotes being a sister lineage to either or both the TACK archaea and Euryarchaeota. Scenario 2 depicts the TACK group as the root of Archaea, with the eukaryotes and Euryarchaeota as sisters. Scenario 3 — the most likely according to the new study — depicts Euryarchaeota as the root of Archaea, with the eukaryotes and the TACK archaea as sisters. Credit: K. Cantner, AGI, after Raymann et al., PNAS, 2015.

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.

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

Tue, 06 Oct 2015 10:14:57 -0400

Mammals, such as the docodonts illustrated here, experienced a burst of rapid evolution in skeletal and dental features in the Middle Jurassic. Credit: April Neander.

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.

Bigger is better in the sea

Mon, 08 Jun 2015 08:33:55 -0400

Anomalocaris was the biggest, baddest predator in the Cambrian ocean. Credit: ©Ghedoghedo, CC BY-SA 3.0.

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.

Bird genomes untangle branches of avian family tree

Tue, 07 Apr 2015 13:24:30 -0400

Birds are one of the most diverse groups of vertebrates on Earth, with more than 10,000 known species. Credit: ©Shutterstock.com/Tom Reichner.

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.

Benchmarks: February 12, 1809: Charles Robert Darwin is born - and so began modern biology