New research offers glimpse into early human development

By LAURA UNGAR
AP Science Writer

Scientists have been able to get a rare glimpse into a crucial, early stage of human development by analyzing an embryo in its third week after fertilization. That’s a moment in time that has been difficult to study because of practical and ethical considerations. Scientists reported Wednesday in the journal Nature that they were able to see a process called “gastrulation,” when new types of cells are formed, in a single embryo that was 16 to 19 days old, donated by a woman who ended her pregnancy. Most women don’t yet know they’re pregnant by this point and decades-old global guidelines have until recently prohibited growing human embryos in a lab beyond 14 days.