Missing Genetic Link in Human Evolution

[gültekin]

http://news.nationalgeographic.com/n...all_fours.html

Five adult siblings who can walk only on all fours have been found in Turkey, researchers say. These human quadrupeds may provide clues to how humans evolved to stand on two feet.
The three sisters and two brothers may offer insight into the way our apelike ancestors moved, according to scientists. Human ancestors are believed to have begun walking on two legs more than three million years ago.

(See "Fossil Pushes Upright Walking Back 2 Million Years, Study Says.")

Discovered in a remote area of southern Turkey last summer, the family of ethnic Kurds has sparked a scientific debate, which will be covered in a BBC television documentary that is set to air on March 17 in the United Kingdom. The family's exact location and last name have not been disclosed.

Born with a genetic brain abnormality, two of the sisters and one of the brothers are thought to have only walked on all fours their entire lives. The two other siblings can walk upright for short distances.

The siblings' parents are closely related and have had 19 children in all.

This bizarre case is not a hoax, according to experts who have studied the family.
The cause of the four-limbed locomotion, however, is a bone of contention among the researchers.

Uner Tan is a neurophysiologist—a doctor specializing in the functions of the brain, spinal cord, and nerves—at Cukurova University in Adana, Turkey.

He believes the siblings, who range in age from 18 to 34, are evolutionary throwbacks—a "missing link" to our forebears. (Related reading: "Was Darwin Wrong?")

Meanwhile German geneticists believe the siblings' genetic abnormality may have knocked out the gene responsible for bipedalism, or two-legged walking, in humans.

http://www.huffingtonpost.com/2014/0...n_5595462.html
http://www.dailymail.co.uk/news/arti...alk-fours.html

[gültekin]

https://en.wikipedia.org/wiki/The_Fa...s_on_All_Fours

The Family That Walks On All Fours is a BBC2 documentary that explored the science and the story of five individuals in the ethnic Kurdish [1] [2] [3] Ulas family in Turkey that walk with a previously unreported quadruped gait.[4] The documentary was created by Passionate Productions and was broadcast on Friday 17 March 2006. The narrator is Jemima Harrison. A revised version of the documentary that shifts the focus away from the story of the discovery of the family and includes the views of additional scientists was shown on NOVA on 14 November 2006.[5]

Debate exists as to the nature and cause of their walking, including controversial speculation in the form of the Uner Tan syndrome that it may be a genetic throwback to pre-bipedal hominid locomotion. Nicholas Humphrey, who accompanied the documentary makers, concluded that it was due to a rare set of genetic and developmental circumstances coming together. First, their mother recalls that initially all of her 19 children started off walking with a bear-crawl (i.e. on their feet rather than their knees). Second, due to an inherited recessive genetic mutation, they have a non-progressive congenital cerebellar ataxia that impairs the balance children normally use to learn to walk bipedally. Not being able to manage the balance needed for bipedal walking, they perfected in its place their initial bear-crawl into an adult quadruped gait.

It should be considered that the defect in these patients likely has nothing to do with genes involved in the human evolution of upright walk. The cerebellum abnormalities makes it more difficult to balance and thus the patients find it easier to use their hands to efficiently move about leading to an unusual adaptation. The documentary highlights problems encountered in societies that provide less early access and continuous health
care for spontaneous genetic variations that lead to impaired brain development.
Synopsis

Strange footprints and footsteps appear: "About four million years ago our distant ancestors did something amazing, something that changed them forever. It is the moment for many that we made the leap from ape to man”.
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