For its first four weeks, a human embryo looks like a crumpled tube. But around its twenty-seventh day of development, four buds bulge from its sides. Over the next few days, the buds grow like tulips, stretching out into flattened stalks and blooming into crowns of fingers and toes. Inside these developing limbs, bones condense. Muscle cells, tendons, blood vessels and nerves all find their respective places. The embryo now has hands with thumbs to suck, legs ready to deliver a kick.
That’s the opening to my latest piece for the New York Times, “From Developing Limbs, Insights That May Explain Much Else.” No meta-commentary on the death of the press. No jousting with the forces of ignorance. Just straight, cool science.
(Some of the papers behind the story: 1, 2, 3, 4)
[Image of limb bud with apical ectodermal ridge marked by arrows: Maria A. Ros]
Originally published April 6, 2009. Copyright 2009 Carl Zimmer.