Sci-ence.org — Science Comics and Writing for the Masses. A Closer Look at Evolutionary Faces. To recreate the faces of our early ancestors, some of whom have been extinct for millions of years, sculptor John Gurche dissected the heads of modern humans and apes, mapping patterns of soft tissue and bone. He used this information to fill out the features of the fossils. Each sculpture starts with the cast of a fossilized skull; Gurche then adds layers of clay muscle, fat and skin.
Seven of his finished hominid busts will be featured at the National Museum of Natural History’s David H. Koch Hall of Human Origins, which opens March 17. They are perhaps the best-researched renderings of their kind. Gurche, a “paleo-artist,” even molds the hominids’ eyes out of acrylic plastic, eschewing pre-fabricated versions. The sculpture above is of Lucy’s species, Australopithecus afarensis, which walked the earth roughly three million years ago.
Not Exactly Rocket Science. Cell Size and Scale. Some cells are visible to the unaided eye The smallest objects that the unaided human eye can see are about 0.1 mm long. That means that under the right conditions, you might be able to see an ameoba proteus, a human egg, and a paramecium without using magnification. A magnifying glass can help you to see them more clearly, but they will still look tiny. Smaller cells are easily visible under a light microscope. It's even possible to make out structures within the cell, such as the nucleus, mitochondria and chloroplasts. Light microscopes use a system of lenses to magnify an image. The power of a light microscope is limited by the wavelength of visible light, which is about 500 nm. To see anything smaller than 500 nm, you will need an electron microscope.
Adenine The label on the nucleotide is not quite accurate. How can an X chromosome be nearly as big as the head of the sperm cell? No, this isn't a mistake. Carbon The size of the carbon atom is based on its van der Waals radius. New Scientist.