ScienceDaily (Apr. 25, 2012) — ICP researchers have discovered one of the first fossil-based evidences supporting the evolutionary theory of aging, which predicts that species evolving in low mortality and resource-limited ecosystems tend to be more long-lived.
The study shows that the tooth height of endemic insular mammals is an indicator of longevity, and questions the use of this morphological characteristic as an exclusive indicator to infer the diet of fossil species, and to interpret the climate in which they lived.
Island systems often function as natural laboratories to test evolutionary hypotheses, since they are less complex than continental systems. Increased longevity of insular endemic species is an adaptation that the evolutionary theory of aging predicts, as part of an evolutionary strategy that pushes the islands’ endemics to a slower life cycle, due to the absence of predators and the limited resources. In this context, Xavier Jordana and the researchers who sign the work published today in the online edition of the Proceedings of the Royal Society B wonder if the increased height of the teeth of herbivores endemic to islands may be an evolutionary response to this longevity. This would call into question the consensus that so far explained this morphological characteristic from differences on diet and climate.
The paper "Evidence of correlated evolution of hypsodonty and exceptional longevity in endemic insular mammals" concludes that indeed Myotragus balearicus, the fossil species chosen for this study, needed higher teeth to get to live as long as it did. Hypsodonty, as experts call having a high dental crown, can be an indicator of long-lived species.
As explained by the ICP researcher Xavier Jordana, lecturer at the Universitat Autònoma de Barcelona in the masters in Human Biologya and in Paleontology and main author of this work, "the study focuses on a fossil species, but our results have implications for herbivorous mammals in general, extinct and extant, and especially in insular endemic species. The latter share some common characteristics, known as the island syndrome, which are different from their mainland relatives, as they evolve in special ecological conditions, such as the lack of predators, high population density and limited resources.”
The research now published analyzes the diet, longevity and mortality patterns of M. balearicus, a fossil bovid endemic to the Balearic Islands. The paper concludes that, despite being extremely hypsodont, M. balearicus was mostly a browser, that fed on leaves and shoots of trees and shrubs, and probably also tubers and roots, which involve excessive abrasion of the teeth because they have to dig into the ground to reach them. They did not have such an abrasive diet as grazers, which feed mainly of grasses and, therefore, exhibit higher teeth. The feeding habits, however, are not sufficient to explain the hypsodonty of Myotragus.
By analyzing M. balearicus longevity from annual growth lines of the teeth cementum, the researchers obtained a calculation of about 27 years, almost doubling that expected for a bovid of such body mass. In addition, the study of mortality patterns in two populations of M. balearicus, one from Cova Estreta and another from Cova des Moro in Mallorca, show juvenile and adult survival rates higher than in extant continental bovids. This means that a large proportion of the population reached greater ages and, therefore, M. balearicus was a species with a slow senescence rate, ie. with late aging.
These results are consistent with the evolutionary theory of aging that predicts the delay of senescence in populations with low extrinsic mortality. In an environment where few external elements can cause death of individuals, such as the lack of predators on an island, the species adapts by changing its aging rate and lifespan. For herbivores one way to do that is to select those individuals in the population with higher teeth, for which senescence starts later.
The fossil genus Myotragus has been an ideal model for evolution studies in islands and M. balearicus is the terminal species, which became extinct about 3,000 years ago. Myotragus survived completely isolated in Mallorca and Menorca for more than 5 million years, from the Pliocene to the Holocene. During its evolution Myotragus underwent significant changes, particularly affecting the locomotor system and its body size, as well as its nervous system and feeding apparatus. Dwarfism, reduced brain size and changes in dentition are the most distinctive evolutionary traits. Many of these morphological features are shared by all the island fauna, as is the case with the increased crown height of the molar teeth.
The study is based on fossil remains of M. balearicus, recovered at different sites of Mallorca, especially Cova Estreta (Pollença), Cova des Moro (Manacor) and Cova Moleta (Sóller). Currently, these fossils are deposited in the collections of the Museum of the Miquel Crusafont Catalan Institute for Paleaontology in Sabadell, and of the Mediterranean Institute for Advanced Studies and the Balearic Museum of Natural Sciences in Mallorca.
"Titanic" director James Cameron dove to the Earth's deepest point in a specially designed submarine, the National Geographic Society said, making him the first man to travel alone to the near 7-mile depth of the Marianas Trench.
The Hollywood icon, also the director of "Avatar" and other films, touched down in the western Pacific Ocean's low point shortly before 8 a.m. Guam time today (Sunday evening in the U.S. East Coast), the Geographic said.
He reached a depth of 35,756 feet and stayed on the bottom for about three hours before he began his return to the surface, according to information provided by the expedition team. He had planned to spend up to six hours on the sea floor.
"Cameron collected samples for research in marine biology, microbiology, astrobiology, marine geology and geophysics," the Geographic said.
He also spent time filming the Marianas Trench, about 200 miles southwest of the Pacific island of Guam.
The trip to the deepest point took two hours and 36 minutes. But Cameron's return aboard his 12-ton, lime-green sub called Deepsea Challenger was a "faster-than-expected 70-minute ascent," according to National Geographic. A helicopter spotted the submersible bobbing in the water and it was brought aboard the ship by a crane.
There were no immediate word on Cameron's physical condition after the dive, but the expedition said he planned a video interview later in the day. A medical team was present when Cameron, 57, emerged from the sub, according to the expedition.
Expedition physician Joe MacInnis told National Geographic News before the journey that recent test dives, including one that went more than five miles deep, had gone well and that he expected Cameron would be fine.
"Jim is going to be a little bit stiff and sore from the cramped position, but he's in really good shape for his age, so I don't expect any problems at all," said MacInnis, a long-time Cameron friend, according to National Geographic.
Cameron also captured still photographs and video, but there was no immediate word on when the images will be released. The Geographic said the expedition is being chronicled for a 3-D feature film for theatrical release and subsequent TV broadcast.
"There is scientific value in getting stereo images because ... you can determine the scale and distance of objects from stereo pairs that you can't from 2-D images," Cameron told the Geographic before the dive.
"This journey is the culmination of more than seven years of planning," said Cameron. "Most importantly, though, is the significance of pushing the boundaries of where humans can go, what they can see and how they can interpret it."
The scale of the trench is hard to grasp — it's 120 times larger than the Grand Canyon and more than a mile deeper than Mount Everest is tall.
"It's really the first time that human eyes have had an opportunity to gaze upon what is a very alien landscape," said Terry Garcia, the National Geographic Society's executive VP for mission programs, via phone from Scotland.
Among the 2.5-story-tall sub's tools were a sediment sampler, a robotic claw, a "slurp gun" for sucking up small seacreatures for study at the surface, and temperature, salinity, and pressure gauges.
Swiss engineer Jacques Piccard and Don Walsh, a U.S. Navy captain, are the only others to reach the spot. They spent about 20 minutes there during their 1960 dive but couldn't see much after their sub kicked up sand from the sea floor.
One of the risks of a dive so deep was extreme water pressure. At 6.8 miles below the surface, the pressure is the equivalent of three SUVs sitting on your toe.
Cameron told the Associated Press in an interview after a 5.1 mile-deep practice run near Papua New Guinea earlier this month that the pressure "is in the back of your mind." The submarine would implode in an instant if it leaked, he said.
But while he was a little apprehensive beforehand, he wasn't scared or nervous while underwater.
"When you are actually on the dive you have to trust the engineering was done right," he said.
The film director has been an oceanography enthusiast since childhood and has made 72 deep-sea submersible dives. Thirty-three of those dives have been to the wreckage of the Titanic, the subject of his 1997 hit film, which is being released in a 3-D version next month.
Coronacollina acula may also help us recognise life elsewhere in the universe
At between 550 and 560 million years old, an animal discovered in South Australia recently is the oldest with a skeleton ever found.
The organism, called Coronacollina acula, was found by a team from the University of California.
The finding provides insight into the evolution of life – particularly, early life – on the planet, why animals go extinct, and how organisms respond to environmental changes.
The discovery also can help scientists recognise life elsewhere in the universe.
Coronacollina acula lived on the seafloor. It was shaped like a thimble with at least four 20 to 40-centimetre-long spikes called ’spicules’ attached. These probably held the creature up.
Its age places it in the Ediacaran period, before the explosion of life and diversification of organisms took place on Earth in the Cambrian, 488 to 542 million years ago.
‘Up until the Cambrian, it was understood that animals were soft bodied and had no hard parts,’ said Mary Droser, lead researcher and a professor of geology at the University of California.
‘But we now have an organism with individual skeletal body parts that appears before the Cambrian. It is therefore the oldest animal with hard parts, and it has a number of them - they would have been structural supports - essentially holding it up. This is a major innovation for animals.’
Coronacollina acula is seen in the fossils as a depression measuring a few millimetres to two centimetres deep. But because rocks compact over time, the organism could have been bigger – three to five centimetres tall. Notably, it is constructed in the same way that Cambrian sponges were constructed.
‘It therefore provides a link between the two time intervals,’ Droser said. ‘We're calling it the “harbinger of Cambrian constructional morphology”, which is to say it's a precursor of organisms seen in the Cambrian. This is tremendously exciting because it is the first appearance of one of the major novelties of animal evolution.’
According to Droser, the appearance of Coronacollina acula signals that the initiation of skeletons was not as sudden in the Cambrian as was thought, and that Ediacaran animals like it are part of the evolutionary lineage of animals as we know them.
‘The fate of the earliest Ediacaran animals has been a subject of debate, with many suggesting that they all went extinct just before the Cambrian,’ she said. ‘Our discovery shows that they did not.’
Results of the study appeared online recently in Geology.