OH 5

OH 5 can also refer to Ohio's 5th congressional district or to Ohio State Route 5.

Zinj or Nutcracker Man

Catalog number	OH 5
Common name	Zinj or Nutcracker Man
Species	Paranthropus boisei
Age	1.75 mya
Place discovered	Olduvai Gorge, Tanzania
Date discovered	July 17, 1959
Discovered by	Mary Leakey

OH 5 (Olduvai Hominid number 5, also known as Zinjanthropus or "Nutcracker Man"; colloquially as "Dear Boy") is a fossilized cranium and the holotype of the species Paranthropus boisei. It was discovered in Olduvai Gorge, Tanzania, by archaeologist-paleontologist Mary Leakey in 1959.

Her husband and fellow scientist Louis Leakey initially classified the hominid as Zinjanthropus boisei and thought that it was an early ancestor of modern humans that lived approximately 2 million years ago. However, this contention was later withdrawn because of its robust australopithecine features and the discovery of Homo habilis soon thereafter.

Discovery

Mary and Louis Leakey had conducted excavations in Tanzania since the 1930s, though most such work was postponed due to the outbreak of World War II. They returned in 1951, finding mostly ancient tools and fossils of extinct mammals for the next few years. On the morning of July 17, 1959, Louis felt ill and stayed at camp while Mary went out to Bed I's Frida Leakey Korongo (korongo is Swahili for gully; this one was named after Louis's ex-wife). Sometime around 11:00 a.m., she noticed a piece of bone that "seemed to be part of a skull" which had a "hominid look".

After dusting some topsoil away and finding "two large teeth set in the curve of a jaw", she drove back to camp exclaiming "I've got him!" They created a pile of stones around the exposed portion of the fossil to protect it from the weather. Active excavation began the following day; they had chosen to wait for photographer Des Bartlett to arrive so that a photographic record of the entire process of removal could be made. A partial cranium was fully unearthed August 6, though it had to be reconstructed from its fragments which were scattered in the scree.

Once he had examined the cranium, Louis determined it to be subadult, or adolescent, based on its dentition, and he and Mary began to call it "Dear Boy". He also believed that it was of a species ancestral to modern humans but a member of the subfamily Australopithecinae. In describing the fossilized hominid in his journal, Louis initially considered the classification Titanohomo mirabilis (wonderful Titan-like man), but he eventually dubbed their find Zinjanthropus boisei (East Africa man). Zinj is an ancient Arabic word for the East African coast; anthropus refers to the fossil's humanlike characteristics; and boisei refers to Charles Boise, who had been making financial contributions to the Leakeys' work since 1948. This classification was eventually revised to Paranthropus boisei, though this remains a matter of contention since the genus Paranthropus is disputed because of morphological similarities to Australopithecus. In either case, 5 is the holotype of its species.

Analysis

Louis wrote "A new fossil skull from Olduvai" for Nature the week following the excavation, detailing the titular find and the "living floor" of Bed I which was replete with fossils of other mammalian fauna. "The Newest Link in Human Evolution: The Discovery by L.S.B. Leakey of Zinjanthropus Boisei", his account of the dig, was published in the January 1960 issue of Current Anthropology. It was annotated by anthropologist Francis Clark Howell, who had been allowed to examine the Leakeys' Olduvai findings before public announcements of their discovery.

Louis also wrote "Finding the World's Earliest Man" for the September 1960 issue of National Geographic, estimating the fossil's age to be 600,000 years old. University of California, Berkeley, geochemists Garniss Curtis and Jack Evernden used potassium-argon dating to re-assess the site, finding that Olduvai's Bed I was actually about 1.75 million years old. Such an application of geochronology was unprecedented; OH 5 became the first hominin to be dated by that method. The same process was used for OH 7, the holotype of Homo habilis (handy man).

External image
Zinj on display at the National Museum of Tanzania.

After the cranium was reconstructed with a model of the absent mandible, contemporaneous newspapers referred to it as "Nutcracker Man" due to the large posterior teeth and jaws which gave it a resemblance to vintage nutcrackers. Phillip Tobias, a colleague of the Leakeys, has also received attribution for this nickname. Primitive tools fashioned out of rocks and bone were excavated at and around Olduvai's Bed I, sometimes called the FLK Zinjanthropus site since the finding of OH 5.

Louis initially believed P. boisei to be a direct ancestor of modern humans (as evident from the title of his National Geographic article) and the maker of those tools found near its remains, but he withdrew this idea once he and Mary unearthed Homo habilis – which had a larger brain – in the same area less than two years later. Despite that, OH 5 made the Leakeys famous and brought more attention to the developing field of paleoanthropology. The cranium was taken to Kenya after its discovery and was there until January 1965 when it was placed on display in the Hall of Man at the National Museum of Tanzania in Dar es Salaam. It remains there as of 2009, still recognized by the name Zinjanthropus, or simply Zinj.

External links

• Images of OH 5
• Archaeology Info