Sperm injection method may be used too much

FERTILITY
For many men with fertility problems, ICSI, or intracytoplasmic sperm injection, is a godsend. The technique, developed in the early 1990s, is used to insert a single sperm directly into an egg, enabling fertilization even if sperm are few or would have trouble penetrating by themselves. But in recent years, ICSI has become standard practice in fertility clinics even when men have no sperm problems, according to a study by University of Illinois researchers. By 2004, the study found, nearly 58 percent of in vitro fertilization procedures included ICSI, even though male infertility remained steady at about 30 percent . ICSI use is particularly heavy in states where infertility treatments must be covered by insurance, including Massachusetts. The study's lead author, Dr. Tarun Jain of the University of Illinois at Chicago, says further research is needed to determine whether such frequent use of ICSI makes sense. Physicians may believe it improves their patients' chances of conceiving, he said, but there is no good scientific data to back up that idea. The technique also has downsides: It can add about $1,500 to the price of fertility treatment; takes up lab time; and there is some concern that it may even result in lower pregnancy rates and possibly a slightly higher rate of birth defects.

BOTTOM LINE: Intracytoplasmic sperm injection is becoming a standard fertility procedure even when men have none of the sperm problems that it was designed to circumvent.

CAUTIONS: The study did not attempt to answer the question of why ICSI has become so common. It could be that clinics see noticeably better results with it, but have not published that data.

WHAT'S NEXT: Researchers hope to determine whether the broad use of ICSI improves a couple's chances of a successful pregnancy and healthy baby.

WHERE TO FIND IT: The New England Journal of Medicine, July 19

CAREY GOLDBERG

EVOLUTION

Humans arose from Africa

Humans evolved in Africa rather than in multiple places around the globe, a new study suggests. The findings may help settle a longstanding debate in which genetic analyses have generally supported a single African origin, while small sets of anatomical data have suggested that evolution might have occurred in several places. Andrea Manica of the University of Cambridge and his colleagues analyzed cranial measurements from 4,666 male skulls and 1,579 female skulls drawn from 105 populations around the world, and determined the degrees of variability among the skulls. The scientists developed a model that found the highest degree of diversity in central/southern Africa, with diversity gradually diminishing with distance from this region. The pattern fits with the single-origin theory, under which diversity lessens as populations disperse since the small, scattering émigré groups have less genetic variation than the original group. Comparing their model with a similar model of genetic diversity, Manica and his colleagues found that the two matched. "If there were other points of origin, you would expect another peak of diversity somewhere," Manica said.

BOTTOM LINE: Humans appear to have originated in one place in central/southern Africa and to have colonized the rest of the world from there.

CAUTIONS: The sample size was not large enough for the researchers to determine if there was one or multiple exoduses from Africa. Each of these scenarios might have led to its own subtle markers in variation patterns that this study could not detect.

WHAT'S NEXT: It is still unclear how humans, after evolving in Africa 200,000 years ago, spread throughout the world in a smooth, homogeneous manner within the last 50,000 to 60,000 years. "It shows they were adept at moving through environments we might have thought of as difficult," Manica said. "Maybe they reached some level of technology, or maybe the climate had changed."

WHERE TO FIND IT: Nature, July 19

AMI ALBERNAZ