MIAMI — Dinosaurs struggled to survive for tens of millions of years before they finally went extinct, an event widely blamed on the environmental fallout from an asteroid strike, researchers say.
The argument offers the latest salvo in a long-running debate among scientists over the state of dinosaur health in their final years on Earth — some say they were flourishing, while others say they were strongly in decline.
For the study in the Proceedings of the National Academy of Sciences, researchers combed through fossil records from around the world and performed a statistical analysis showing that various species of dinosaurs were going extinct at a faster pace than new ones were emerging for a period of at least 40 million years prior to the cosmic debris that smashed into what is modern-day Mexico.
“We were not expecting this result,” lead author Manabu Sakamoto, a paleontologist at the University of Reading, said.
“While the asteroid impact is still the prime candidate for the dinosaurs’ final disappearance, it is clear that they were already past their prime in an evolutionary sense.”
For instance, long-necked vegetarian sauropod dinosaurs — the largest land animals known to exist — were in the fastest decline, the study found.
But the ropods, the group that includes the iconic, meat-eating Tyrannosaurus rex, were disappearing at a more gradual pace.
Factors in their struggle likely included the break-up of continental land masses and sustained volcanic activity, the study said.
Then, a giant asteroid collided with the Earth — known as the Chicxulub impact in Mexico — 66 million years ago, causing a massive dust storm that blocked the Sun and led to a period of global cooling and widespread plant deaths.
Without trees and vegetation, an important food and shelter source disappeared, and so did the dinosaurs.
“This suggests that for tens of millions of years before their ultimate demise, dinosaurs were beginning to lose their edge as the dominant species on Earth,” Dr Sakamoto said.
Even more, the research offers a look into the future. With many species already struggling due to human-driven climate change, those on the edge may be completely wiped out in the event of a disaster.
“Our study strongly indicates that if a group of animals is experiencing a fast pace of extinction more so than they can replace, then they are prone to annihilation once a major catastrophe occurs,” Dr Sakamoto said.
“This has huge implications for our current and future biodiversity, given the unprecedented speed at which species are going extinct owing to the ongoing human-caused climate change.”
Sleeping in on weekends may help live longer
Sleep deprivation has been found to have numerous negative effects on a person’s health. But the new study has shown that sleeping more on the weekend might help ease health problems associated with not getting enough during the week, and even reduce the risk of an early death.
The study, published in Journal of Sleep Research by scientists from Sweden and the United States, suggested that the negative effects of a few nights of short sleep could be counteracted by staying in bed over the weekend.
The from the Stress Research Institute (SRI) at Stockholm University and the Karolinska Institute discovered that people below 65 years old who slept less than five hours on weekends had a higher risk of early death after examining medical and lifestyle data from more than 43,000 adults, following them for a period of 13 years.
For people who slept for less than five hours throughout the week but slept longer on the weekends for about nine hours, there was no increase in mortality risk. But, for people who consistently slept for less than five hours through the whole week, the mortality risk is higher.
Torbjorn Akerstedt, one of the authors of the research and a clinical neuroscience professor from the Karolinska Institute in Sweden, said that the findings were consistent with previous studies on the link between sleep duration and mortality.
However, those previous studies only focused on sleep during weekdays.
“The results imply that short sleep is not a risk factor for mortality if it is combined with a medium or long weekend sleep,” the researchers wrote in the study.Follow @gorkhapost