Mitochondrial DNA of archaic humans has been retrieved from cave sediments, but it has limited value for studying population relationships.
Over their entire late-Cretaceous reign, the total number of Tyrannosaurus rex that ever lived on Earth was roughly 2.5 billion individuals, according to a new study, which leveraged the relationship between body mass and population density observed in living animals to estimate the population traits of the iconic, long-extinct species.
Coral reefs provide many services to coastal communities, including critical protection from flood damage. A new study led by researchers at the University of California, Santa Cruz, and the US Geological Survey reveals how valuable coral reefs are in protecting people, structures, and economic activity in the United States from coastal flooding during storms.
A lot of attention has been paid in recent years to the carbon footprint of the foods we eat, with much of the focus on the outsize contribution of meat production and especially beef.
With fossils few and far between, paleontologists have shied away from estimating the size of extinct populations. But UC Berkeley scientists decided to try, focusing on the North American predator T. rex. Using data from the latest fossil analyses, they concluded that some 20,000 adults likely roamed the continent at any one time, from Mexico to Canada. The species survived for perhaps 2.5 million years, which means that about 2.5 billion lived and died overall.
The ability to grow the cells of one species within an organism of a different species offers scientists a powerful tool for research and medicine. It's an approach that could advance our understanding of early human development, disease progression and aging, and also holds promise for organ transplantation and for testing therapeutics. Salk researchers have now come one step closer toward this goal by demonstrating a new integration of human cells into animal tissue.
Mammal communities underwent long periods of so-called functional stability despite the waxing and waning of their constituent species over tens of millions of years, even persisting through several environmental crises. This is the main conclusion of a new study published in the renowned journal Science by an interdisciplinary team from Spain and Germany.
Bearded dragon embryos can use two different sets of genes to become a female lizard -- one activated by the sex chromosomes and the other activated by high temperatures during development. Sarah Whiteley and Arthur Georges of the University of Canberra report these new findings April 15th in the journal PLOS Genetics.
Investigators in China and the United States have injected human stem cells into primate embryos and were able to grow chimeric embryos for a significant period of time--up to 20 days. The research, despite its ethical concerns, has the potential to provide new insights into developmental biology and evolution. It also has implications for developing new models of human biology and disease. The work appears April 15 in the journal Cell.
Only between 2% and 3% of the Earth's terrestrial surface can be considered ecologically intact, according to a new study published in Frontiers in Forests and Global Change. This percentage is drastically lower than past assessments, which estimated it to be between 20% and 40%, because it factored in loss of species from intact habitat as well as reduced populations of species. A restoration focus of specific species in intact habitat could recover ecological integrity to about 20% of land.