4 Cool Paleontological Discoveries In 2018
Fossils have taught us an enormous amount about the history of life on Earth, but there are always new things to find. Here is a highly subjective selection of the best discoveries of the year.
The ancestor of all life lived at least 3.9 billion years ago
All living organisms are related, which means they all descend from the Last Universal Common Ancestor: a mysterious organism that lived early in Earth's history. LUCA, as it's known, must have been a single-celled organism, somewhat like a bacterium.
A study published in August argued that LUCA lived at least 3.9 billion years ago, no more than 600 million years after the Earth formed.
Holly Betts at the University of Bristol and her colleagues compared the sequences of 29 genes across 102 species. They used that data to build a family tree, showing the order in which new groups split away from their relatives. Then they added dates from the geological record, which allowed them to estimate roughly when the various splits happened.
LUCA cannot be any younger than 3.9 billion years, the team reported. It could be considerably older, the maximum being about 4.5 billion years ago when the Earth formed and, soon after, a huge rock smacked into it and formed the Moon.
In this case, the genetics is revealing something the fossil record cannot. The oldest accepted fossils of living organisms are just 3.4 billion years old. Putative fossils from 3.7 billion years ago were reassessed this year, and it seems they were just peculiar folded rocks.
Animals with backbones emerged in shallow seas near the shore
Creatures with backbones are known as vertebrates. They include all fish, amphibians, reptiles, birds and mammals - including humans. So figuring out how and why the first vertebrates evolved is one of the biggest questions in paleontology.
In a study published in October, Lauren Sallan at the University of Pennsylvania and her colleagues compiled a database of nearly 3000 fish fossils from 480 to 360 million years ago. All the earliest vertebrate fossils were found in near-shore environments, such as tidal zones and lagoons. It was their descendants that moved out to colonise the wider, deeper ocean.
It's not clear why shallow seas acted as a cradle for the first vertebrates. It may be that the endless crashing waves near the shore acted as a selective pressure on animals to evolve tougher skeletons. A backbone stiffens an animal's entire body, which may have offered greater resilience.
The "first bird" Archaeopteryx really could fly, just not very well
Archaeopteryx is one of the most famous fossils ever discovered. The first specimens turned up just a few years after Darwin published Origin of Species, in which he set out his argument that new species evolve by natural selection. A fossilised "dino-bird" that had feathers and wings, but also had a toothed snout instead of a beak, and claws on its wings, was a perfect example of evolution in action. Later fossil discoveries, particularly from China, have revealed that Archaeopteryx was just one of a huge radiation of primitive birds, but it remains a crucial species.
Given its status as one of the first birds, it often surprises people to learn that paleontologists have long argued about whether or not it could actually fly. It had wings and feathers, but so do penguins and you don't see them taking to the skies. The question was whether it had gone far enough down the evolutionary road towards being a proper bird. Was its skeleton set up in such a way that it could flap its wings with enough force to take off?
According to a study published in March, the answer is: "kind of". Dennis Voeten of the ESRF, the European Synchrotron facility in Grenoble, France and his colleagues scanned an Archaeopteryx skeleton and found that its wing bones were set up for active flight. But it probably couldn't fly any great distance. Instead, it could take off for short bursts, perhaps to escape predators. Imagine a pheasant being flushed out by a fox, briefly hurtling up into the air to get to safety before returning to earth a short distance away, and you will have the idea.
An extinct bird from Madagascar was the largest bird ever to exist
Birds today can get pretty big. The ostrich is the heaviest living bird, regularly topping 100 kilograms, while the wandering albatross has the largest wingspan at over 3 metres.
However, in the past birds were bigger. The heaviest group seems to have been the elephant birds, which lived on Madagascar off Africa's east coast and resembled giant ostriches. They died out around 1000 years ago. It's not clear why, but humans were on Madagascar by then so we may have had something to do with it.
In a study published in September, James Hansford and Samuel Turvey of the Zoological Society of London, UK examined 346 specimens of elephant bird. As well as sorting out how the various groups were related, they identified a new species, which they dubbed Vorombe titan. Its average body mass was 650kg, far more than any ostrich and larger than any known extinct bird.
What's more, the pair examined a V. titan femur that was too incomplete to be included in their analyses. Based on its circumference, the animal it belonged to could have weighed 860kg, making it the largest individual bird ever found.
This doesn't change our understanding of the evolutionary story much; I just think giant birds are cool.