In its first week, a fertilized human egg develops into a hollow ball of 200 cells and then implants itself on the wall of the uterus. Over the next three weeks, it divides into the distinct tissues of a human body.

And those crucial few weeks remain, for the most part, a black box.

“We know the basics, but the very fine details we just don’t know,” said Jacob Hanna, a developmental biologist at the Weizmann Institute of Science in Israel.

Continue reading “Scientists Debut Lab Models of Human Embryos” →

One of the greatest transformations in the history of life occurred more than 600 million years ago, when a single-celled organism gave rise to the first animals. With their multicellular bodies, animals evolved into a staggering range of forms, like whales that weigh 200 tons, birds that soar six miles into the sky and sidewinders that slither across desert dunes.

Scientists have long wondered what the first animals were like, including questions about their anatomy and how they found food. In a study published on Wednesday, scientists found tantalizing answers in a little-known group of gelatinous creatures called comb jellies. While the first animals remain a mystery, scientists found that comb jellies belong to the deepest branch on the animal family tree.

Continue reading “Bizarre Sea Creatures Illuminate the Dawn of the Animal Kingdom” →