September 12, 2013

Tuberculosis (TB), a major cause of death in developing countries, may be so hard to defeat because it likely originated among our ancestors in Africa more than 70,000 years ago. In fact, it may have originated even before modern people migrated from the continent, according to a new study by an international team of scientists led by Sebastien Gagneus, an expert on infectious diseases from the Tropical and Public Health Institute in Basel, Switzerland. For their study, the scientists examined DNA sequences of tuberculosis bacteria from 259 subjects throughout the world. These genetic analyses enabled the scientists to construct a “family tree” of the bacterium, tracing its history through time.

A little more than a century ago, TB ranked among the most common causes of death in the world. Rod-shaped bacteria called tubercle bacilli cause the disease. Tubercle bacilli belong to a genus (group) of bacteria called Mycobacterium. Today, improved methods of prevention, detection, diagnosis, and treatment have greatly reduced the number of people who get the disease and those who die from it. However, even today tuberculosis claims many lives in countries where these improved methods are not widely available.

Evolutionary scientists believe that anatomically modern humans first appeared in Africa during the past 100,000 years. Sometime before about 50,000 years ago, they migrated out of Africa to other parts of the world. The new research suggests that early modern humans suffered from tuberculosis and carried the bacterium with them on their journeys. The scientists believe that the TB bacterium’s ability to go dormant (inactive) for long periods enabled the deadly disease to spread with human populations across the globe.

A volunteer physician with Doctors Without Borders, an international relief organization, treats a patient in Kenya for tuberculosis. (AP/Wide World)

Scholars had long thought that human tuberculosis, which cannot survive or infect any other animal, was a relatively recent disease. They believed that human TB originated from tuberculosis varieties that affect animals, such as cattle. Over the past 10,000 years, as humans developed agriculture and began domesticating animals, scientists believed the tuberculosis bacterium was passed to humans from livestock. Bovine tuberculosis, which affects cattle and can sometimes infect humans, seemed to support this view. The new research, however, indicates that tuberculosis was established in human populations long before people began keeping livestock.

Additional World Book articles:

• BCG
• Calmette, Albert
• Trudeau, Edward Livingston
• Tuberculosis: An Old Foe Gains Ground (a special report)

May 25, 2012

A new search for the legendary creatures known as Bigfoot and the Yeti is being mounted by several researchers from Oxford University in the United Kingdom and the Lausanne Museum of Zoology in Switzerland–but they don’t plan to leave their laboratories. Instead of trekking through dense forests or crossing snowy mountains, the researchers plan to use sensitive DNA analysis on samples of hair, blood, and other remains that could have come from the creatures. The researchers are asking wildlife scientists, museums, and Bigfoot enthusiasts to send them written descriptions and photos of any evidence they might have of the creatures. If the descriptions look promising, the researchers will request the physical samples and then test their DNA to determine which species the samples came from. Finding DNA from an unknown primate–the group of mammals that includes monkeys, apes, and human beings–could be evidence that Bigfoot lives and would rank as one of the greatest zoological discoveries in history. “I’m challenging and inviting the cryptozoologists to come up with the evidence instead of complaining that science is rejecting what they have to say,” said geneticist Bryan Sykes of Oxford in an interview. Cryptozoology is the scientific investigation of legendary creatures.

Bigfoot, shown here in an artist's depiction, is a humanlike creature said to live in the Pacific Northwest of the United States and Canada. The creature is said to resemble a large ape--with thick fur, long arms, powerful shoulders, and a short neck--but to walk upright like a human being. (World Book illustration)

Bigfoot is a giant apelike creature said to live in forested regions of North America. Stories of this creature appear in American Indian traditions, where the creature is known as Sasquatch. Thousands of people have reported seeing Bigfoot or finding its footprints in North America, but conclusive proof of its existence has yet to be found. Reports of a similar creature come from the Himalaya range of Asia. This creature is called the Yeti or the Abominable Snowman. In 1951, the British explorer Eric Shipton took pictures of “Yeti” tracks near Mount Everest. Since then, several expeditions, including one sponsored by World Book in 1960, have searched for the creature without success.

A few scientists think it is possible that such a large primate could have survived undiscovered in the dense and remote forests of North America and Asia. One theory suggests Bigfoot and the Yeti are small relic populations of primate thought to have gone extinct. Candidates for Bigfoot include such extinct prehistoric humans as Neandertals or Denisovans, a mysterious species that died out in Siberia 40,000 years ago. Another theory suggests that Bigfoot and the Yeti may be surviving populations of Gigantopithecus, a huge ape that lived in the forests of what are now southern China, Vietnam, and northern India. Gigantopithecus, which is believed to have died out 200,000 years ago, was the largest ape to have ever lived.

The Yeti, also called the Abominable Snowman, is a creature said to live on Mount Everest and other mountain ranges of Asia. According to legend, the Yeti is a hairy beast with a large, apelike body and a face that resembles that of a human being. It has long arms that reach to its knees, and it walks erect on its thick legs. (World Book illustration)

Scientists with the Bigfoot DNA project will begin by testing an archive of remains stored at the Lausanne Museum that were assembled by cryptozoologist Bernard Heuvelmans, who investigated reported Yeti sightings from 1950 until his death in 2001. Many sensational reports of Bigfoot remains have been exposed as hoaxes and fakes in the past. The researchers in this project point out that DNA evidence cannot be faked. They expect to published their results in science journals.

Additional World Book articles:

• Shipton, Eric Earle
• Journey to the Top of the World (a Special Report)

Fossil skeletons of two primates who lived 1.97 million years ago may represent the oldest known direct ancestor of modern human beings, according to a report by scientists from South Africa. The fossils have been given the scientific name Australopithecus sediba.  They were discovered between 2008 and 2010 at Malapa, a cave site in South Africa, by paleoanthropologist Lee Berger from the University of the Witwatersrand in Johannesburg. Australopithecines were a group of early humanlike creatures that lived in Africa from about 4 million to about 1 million years ago.

The fossils include bones from two individuals-an adult female and a juvenile male. They were found close together, suggesting that they may have died together, perhaps by falling into an underground cavern. The fossils include nearly complete skulls, portions of the hipbones, and a rare collection of bones from the hands and feet.  The skulls show A. sediba had a small brain, about the same size as that of a chimpanzee. But a detailed study of the inside of the skull shows that the front of the brain was much more humanlike than apelike.

The hipbones are short and wide, more like those of a modern human. Anklebones and a nearly complete right hand from the adult female are nearly identical to those of a modern person, only smaller. These features show that A. sediba could walk like a modern human and could have made  and used stone tools.

Berger and his colleagues argue that A. sediba was more like a modern person than Homo habilis, another species of early human that originated in Africa around 2 million years ago. They claim that A. sediba represents a direct link between the apelike australopithecines and Homo erectus, a species that appears a bit later. Most scientists think Homo erectus was a direct ancestor to Homo sapiens, the species that includes all people living today.

Additional World Book articles:

• Prehistoric people
• Stone Age
• Homo florensiensis