Pre-Clovis archaeological sites of the Americas 5: Nugget Gulch, Klondike, Yukon Canada

Pre-Clovis archaeological sites of the Americas 5 Nugget Gulch, Klondike, Yukon Canada

 
An interesting paper from Harington and Morlan from 2002: Evidence for a Human Modification of a Late Pleistocene Bison (Bison sp.) Bone from the Klondike District, Yukon Territory, Canada¹
 
Abstract
A 31000BP Bison limb bone from Nugget Gulch near Dawson City, Yukon, shows a “ring crack” considered to be a human-made impact mark resulting in exposure of marrow. This bone is approximately contemporaneous with wolf, horse, and Dall sheep specimens found on ancient Mid-Wisconsinian terrain surface at this locality. Similar ring cracks, also interpreted as human-made, have been noted on late-glacial bison bones from Engigstciak, Yukon, and Lost Chicken Creek, Alaska.
 
Here’s the bone in question:

 

The site was discovered when Harington, acting on information received by placer miners had reported what turned out to be Pleistocene mammal bones in the same area, the previous summer to Harington. He noted that the first find of bones lay on what appeared to be an ancient grassy surface lying at approximately 9m below present ground level. Also noted was the fact that those bones lay close to an extensive volcanic ash layer of unknown relationship with the land surface. The bone in the current paper was discovered when Harington returned the following summer to survey the area in more detail.

 

The ancient land surface was exposed when heavy jets of water had been used to remove approximately 9m of frozen organic silt (locally known as “muck”) form the gold-bearing gravels lying on the bedrock, just below the ancient land surface.

Fortuitously 100m downstream, an outcropping of a thin layer of volcanic ash lay some 10cm below the, ancient ground surface. The authors also give the chemical  composition of the tephra/volcanic ash from the site and show the stratigraphy of the site fits with known, dated volcanic layers in the region. This was radiocarbon dated to approximately 50000BP. Thus a lower limit in age was established for the bone.

Bone description:

“The Bison bone is the proximal end of a right radio-ulna near the semilunar notch. Presumably it represents a steppe bison (Bison priscus), a species that was relatively common in the Yukon and Alakka during the mid-wisconsinian interglacial.

The bone has a complex taphonomic history. We believe it was broken by dynamic loading, because it exhibits an oval ring-crack on the anterior surface of the radius adjacent to the proximal epiphysis (Figs 2, 3). Helical fractures radiating distally from the ring crack travelled 14cm along the radius shaft and passed through the ulna that is firmly fused to the radius. Despite the proximity of the ring crack to proximal end,, the fracture did not initially pass through the epiphysis, as the cancellous tissue absorbed the shock. The fracture surfaces form acute and obtause angles with the outer surfaces of the bone, and they exhibit no peturbations caused by split lines. The fracture surfaces are the same colour (pale brown,..) as the outer surface of the bone. These characteristics indicate that the bone was fresh when the fracture occurred.

Also when the bone was fresh, the proximal border of the olecranon process was removed, leaving a continuous row of short chipping scars and a scooped out area of cancellous tissue. Thereafter the bone was buried in the active layer for some time, during which plant roots etched the surface in a few scattered locations. Once deeply buried, the bone became premineralised, probably through the absorption of manganese and iron.”

The authors then explain how the bone was quite fragile when exposed by mining activity and became somewhat cracked and bleached by sunlight.
 

The authors then explain why the marks found on the bone, are, in their opinion of human origin. They say the simplest explanation for the marks on the bone might be that it was gnawed by a large carnivore, however many features of the damage make it much more likely that it was altered by humans. Their explanation consists the following points:

·         The chipping and scooping of the olecranon process lacks any tooth marks

·         The ring crack represents dynamic loading, i.e. a blow, whereas application of force carnivore by biting is a static force

·         The ulna-radius assemblage had an 8cm span, thus the gape of the carnivore would have to encompass this area, it the damage was caused by gnawing there must be concurrent marks on the bone from other teeth. There are none. Even a Short-Faced Bear (the area’s largest Pleistocene predator) could not have caused the damage

·         The size of the ring crack at 32x25mm is too large for the canine of any predator and too small for hoof trampling

·         To cause the damage on the anterior (rear) surface of the bone, an unusual position for a break of this type, the limb would have to be held by the attacker and struck with cobble, presumably to reach the bone marrow.  This also accounts for the loss of the lower portion of the bone.

 

The authors admit that there are no archaeological remains to support the attribution of the bone damage to human agency, but in support of their argument, cite other examples of identically fractured bone from the region that have been accepted as the work of humans.

 

Verdict: Man hunted Mammoth 31000BP in northern North America.

 

Reference

1. Harington, C.R. and Morlan, R.E. 2002. Evidence for Human Modification of a Late Pleistocene Bison (Bison sp.) Bone from the Klondike District, Yukon Territory, Canada. Arctic Vol. 55 No. 2 (June 2002) P. 143-147.