Recent Science Discoveries, 2000

A team of researchers have discovered that when a snowflake falls onto a body of water, it deposits a tiny amount of air just beneath the surface. Before the bubble reaches the surface and pops, it sends out a piercing sound. This sound, ranging from 50 to 200 kilohertz, is too high-pitched to be heard by human ears, which generally pick up nothing higher than 20 kilohertz. However, to porpoises and other aquatic animals that can hear the higher frequencies, the falling snowflakes create an enormous racket just below the surface. Falling snow can add 30 decibels to underwater noise levels. Beyond its deafening impact on water animals, snowflake noise can create “electronic clutter” for people who use sensitive sonar devices.

In March 2000, a team of researchers led by Northern Illinois University paleontologist Dan Gebo announced their discovery of the fossil bones of 45-million-year-old monkeylike primates, the smallest primates ever found. The new species, named Eosimias (“dawn monkey”), was discovered in a limestone quarry in eastern China.

Its foot bones are the size of grains of rice, and it weighs less than a dozen paper clips. Yet the miniature “Dawn Monkey” could represent an evolutionary link between lower primates and higher primates, a group that includes apes and humans. The structure of its tiny ankle bones suggests that it could walk flat-footed, using all four legs, like advanced primates. Unlike advanced primates, however, it probably “didn't have a lot of time to be social,” guesses one scientist. That's because the little animal had to spend most of its time eating to feed its high-speed metabolism–when it wasn't trying to avoid being eaten by bigger creatures. The discovery of this specimen in Asia suggests that our earliest ancestors did not live in Africa alone, as previously thought.

The researchers said that the minute mammals were tree dwellers that relied on a steady diet of insects, fruit, and nectar to fuel their high metabolisms. Unlike contemporary higher primates, the tiny primates likely were nocturnal and solitary creatures.

Astronomers from the National Science Foundation's National Solar Observatory have discovered a “solar heartbeat” in the motion of the layers of gas circulating beneath the Sun's surface. Their research shows that some parallel layers speed up and slow down rhythmically about every 16 months. This internal cyclic action may explain the formation of sunspots and solar flares.

The Sun is not a solid object–it is made up of layers of gas. Unlike Earth, all points on the solar surface do not rotate at the same rate. Its equatorial region rotates once every 27 days, while the regions at the Sun's poles rotate at a slower rate of once every 35 days. The “differential” rotation extends through the Sun's turbulent convective layer, located about 130,494 miles (210,000 kilometers) below the surface, nearly one-third of the distance to the solar core. At the edge of the convective layer, the rotation period varies, completing a cycle about every 15—16 days. Astronomers think that the patterns of these internal movements are connected to the cycles of eruptions seen on the surface.

Geoscientists at the Geological Survey of Western Australia and the Australian National University discovered the world's fourth-largest asteroid impact crater in western Australia. Buried beneath the red-sand country east of Shark Bay, the huge crater centered on Woodleigh Station is estimated to be 75 miles (120 kilometers) in diameter. It is the result of a massive 3.1-mile- (5-kilometer-) wide asteroid that smashed into Earth some 200—360 million years ago. The impact would probably have resulted in an extinction event similar to the Chicxulub impact in the Gulf of Mexico, which has been linked to the extinction of the dinosaurs at the end of the Cretaceous period, 65 million years ago.

The Woodleigh crater's estimated age probably coincides with one of three extinction events known in the fossil record: the Late Devonian extinction (364 million years), the end of the Permian period (247 million years), or the end of the Triassic period (214 million years).

In April 2000, scientists at the University of Witwatersrand, South Africa, announced the discovery of two early hominid fossils excavated in the Sterkfontein caves, 4 miles (7 kilometers) northwest of Johannesburg. The fossils comprise the most complete female skull ever found of her species, together with the lower jawbone of a male. The 1.5- to 2-million-year-old pair were christened Orpheus and Eurydice (after the ancient Greek mythological lovers). They were identified as Paranthropus (“beside man”) robustus, a type of Australopithecine (“ape man”) known for its huge teeth. They were not direct descendants of modern humans but were a line of hominids that became extinct about one million years ago.

For the first time, scientists now know what a male and female Paranthropus looked like and what the differences were between male and female skulls. The top of the male's skull features a ridge, called a sagittal crest, to which the muscles of the lower jaw were anchored. The female, apart from being smaller than the male, has no such crest–a distinction echoed among male and female gorillas today.

Orpheus and Eurydice were largely vegetarians but may have included some meat in their diet from scavenged kills. They may even have used tools.

Astronomers using the world's most powerful radio telescope at Arecibo, Puerto Rico, have captured radar images of a giant, dog-bone—shaped asteroid located in the main asteroid belt between Mars and Jupiter. They are the first images ever made of a main-belt asteroid. The unusual space rock, named 216 Kleopatra, measures about 135 miles (217 kilometers) long and about 58 miles (94 kilometers) wide, roughly the size of the state of New Jersey.

Although the massive asteroid was discovered in 1880, its peculiar dog-bone or distorted dumbbell-like shape was unknown until now. Its strange appearance could have been produced by an incredibly violent collision between two asteroids that did not completely shatter and disperse all the fragments. Or it may once have comprised two separate lobes in orbit around each other with empty space between them, and subsequent impacts filled in the space with debris.

Radar observations of Kleopatra seem to indicate that its surface is porous and loosely consolidated. Its interior appears to be composed of mostly solid metal fragments, possibly an nickel-iron alloy.

A team of Georgian, German, French, and U.S. researchers reported finding a nearly complete fossil cranium and another skullcap representing the earliest known human ancestors from Eurasia, at a site in Dmanisi, Georgia. The 1.7-million-year-old fossils are the first discovered outside of Africa that show clear signs of African ancestry.

Their age and skeletal characteristics link them to the early African species Homo ergaster, a species that some scientists believe is the African version of Homo erectus. The new evidence suggests that they may have been the first hominid species to journey out of Africa.

Stone tools of the less sophisticated “pebble-chopper type,” predating the Acheulean or hand-ax tradition, were found in the sediment with the skulls, contradicting the theory that early humans didn't leave Africa until after they had invented technically advanced tools. Despite the ready availability of raw material, all of the Dmanisi artifacts found at the site are of a pre-Acheulean type that appeared in Africa as early as 2.4 million years ago. Stone Age tools featuring hand-axes, cleavers, scrapers, and sharp stone flakes are called Acheulean (from St. Acheul in France).