LEICESTER, England, Jan. 23 (UPI) -- British geologists suggest humans have so changed the Earth that the planet has ended its Holocene era and has entered a new epoch -- the Anthropocene.

Jan Zalasiewicz and colleagues at the University of Leicester said Nobel Prize-winning chemist Paul Crutzen, in 2002, suggested the Earth had left the Holocene and started the Anthropocene era because of the global environmental effects of increased human population and economic development.

The researchers said they have now documented a radical, yet compelling, case for the idea that the appearance of humans has so physically changed Earth that there is no organic justification for linking pre- and post-industrialized Earth within the same epoch -- the Holocene.

The scientists said their findings present the scholarly groundwork for the formal adoption by the International Commission on Stratigraphy of the Anthropocene as the youngest epoch of, and most recent addition to, the Earth's geological timescale.

The research is presented in the journal Geology.

Mouse study may explain human infertility

LIVERPOOL, England, Jan. 23 (UPI) -- British scientists have discovered an evolutionary phenomenon that occurs in mice and might explain human infertility.

University of Liverpool researchers, in collaboration with Charles University in the Czech Republic, found field mice sacrifice some of their immunity protection in favor of a more rapid fertilization process. That occurs due to the absence of a protein called CD46.

The researchers said field mice have lost their ability to produce the protein -- present in both animals and humans -- resulting in instability of a cap-like structure called the acrosome that's present above the head of sperm cells. The instability allows the acrosome to be shed, creating a surface essential for sperm to be capable of fusing with an egg.

"By improving our understanding of defects in CD46 we may improve treatments for infertility in men," Professor Peter Johnson said. "Humans normally produce a single egg each month and there is no evolutionary necessity to develop rapid sperm reaction to egg fertilization. The process is, therefore, much slower and so any defect in CD46 could result in sperm being destabilized too early."

The study is published in the journal Reproduction.

Cell study may lead to new cancer drugs

BALTIMORE, Jan. 23 (UPI) -- U.S. scientists have discovered a previously unsuspected mechanism of cell death that might lead to stronger, yet less-harmful, anti-cancer drugs.

The Johns Hopkins University researchers determined a cellular stress-response protein prevents cells from dying by interacting with a particular signaling protein and mediating its response to some conventional anti-cancer drugs.

"A major hang-up in cancer chemotherapy is the toxicity caused by DNA disruption of cell division throughout the body," said Dr. Solomon Snyder, a neuroscience professor. "Our research suggests that drugs like cisplatin and novobiocin kill cells as much from this newly discovered mechanism as any other mechanism of cell death.

"Targeting this new mechanism in drug design might make for therapies with fewer side effects," he added.

The research, funded by a U.S. Public Heath Service grant, appeared in last week's early online edition of the Proceedings of the National Academy of Sciences.

Global warming might affect lizard gender

AMES, Iowa, Jan. 23 (UPI) -- A U.S. researcher has discovered egg incubation temperatures have an effect on Australian reptiles.

Iowa State University biologist Dan Warner spent four years in Australia studying the "jacky dragon" lizard to discover if egg incubation temperature and gender affects the viability of the lizards.

In mammals, gender is determined by the chromosomes an embryo inherits from the father. But in some reptiles, gender is determined by temperatures the embryos experience.

Warner tracked male and female lizards born at different temperatures and measured how well they reproduced. In the "jacky dragon," males are born at about 77 to 86 degrees Fahrenheit, while females are born at temperatures both above and below that range. Because some temperatures only produce one gender, Warner had to reverse the sex of some of the embryos using hormones.

Warner discovered "jacky dragons" thrive when they are born at the right temperatures for their gender. He found both males and females reproduce more when exposed to the correct egg incubation temperatures.

He said his findings might have grave consequences for the species if temperatures increase in the parts of Australia where the lizards live.

The study appears in the journal Nature.