Terminal Pleistocene epoch human footprints from the Pacific coast of Canada

1. What they did

Very little is known about people living on the Pacific coast of Canada at the end of the last ice age, although this coast is one of the routes people may have taken into the Americas. On Calvert Island, British Columbia, earlier work showed that sea level was only 2 to 3 metres lower than today between 14,000 and 11,000 years ago. So the shoreline of that time lies just under today’s beaches. The researchers dug test holes beneath the beach in front of an archaeological site (EjTa-4) to look for remains from that period.

• First find (2014). In a small test hole, they found a suspected human footprint about 60 cm below the beach, pressed into a light brown clay and filled with dark sand and gravel. Wood at the bottom of the print was radiocarbon dated.
• Excavation (2015 and 2016). They opened a 4 x 2 m area around the first test, digging by trowel layer by layer, and exposed the old ground surface the tracks were made in.
• Recording the tracks. They measured each footprint (length from heel to the second toe, and the width of the ball of the foot), noted which foot it was and its condition, measured its direction, and photographed it. Photos were digitally enhanced to make faint features easier to see.
• Dating and context. They dated wood and charcoal from the track surface, from the bottom of the prints and from the layers above, and studied the sediments, microfossils, wood and stone tools to work out how the site formed.

A field crew of archaeologists, representatives of the Heiltsuk and Wuikinuxv First Nations, and University of Victoria students did the work.

2. What they found

The tracks

• 29 human footprints were recorded, facing in different directions. Some were clear, with visible toes; others were faint.
• Many more partial, footprint-like hollows were seen, but repeated trampling had made them too unclear to record with confidence, so they are not counted.
• Several tracks had clear rims where the clay had been pushed sideways by the foot. Modern boot prints on the same beach form the same kind of rim after one tide.
• Pits from old tide pools and root disturbance had destroyed parts of the track surface, so most prints were in the northern part of the excavation.

Who made them

• 18 tracks could be fully measured. Their sizes fall into three clusters, suggesting at least three people. In modern US shoe sizes, these match about a junior 8, a junior 1 (or a woman’s 3), and a woman’s 8 to 9 (or a man’s 7 to 8).
• Visible toe marks suggest the people were barefoot. Track #4 showed no clear toes, but the enhanced photo revealed drag marks from the first and second toes, so this foot was probably bare too.
• Some prints were stretched where the walker slipped forward on the wet clay.

What the tracks show

• The prints do not form a line of steps (a trackway). They look more like a congregation site, where people gather around an activity.
• Most people were facing north to northwest, up the beach towards the vegetation line. Tracks #8 and #9 are a left and a right print side by side, as if someone stood with feet slightly apart, facing inland with their back to the prevailing wind.

Age

• Shore pine wood pressed into the bottom of the prints and lying on the track surface dates to between 13,317 and 12,633 years ago.
• The sand layer directly over the tracks gave mixed dates (12,640 to 5608 years ago), probably because roots and erosion disturbed it. A clay layer above it dates to about 12,850 to 12,750 years ago.
• Stone tools were found on the track surface, including flakes, cores, pebble tools and retouched tools.

3. What they concluded

• The footprints are certainly human: they show arches, balls, offset heels, and in some cases toes, surrounded by displacement rims.
• They date to the late Pleistocene, about 13,000 years ago (a conservative range of 13,317 to 12,633 years ago), and were left by at least three people, including one juvenile.
• The people may have stepped ashore from boats and walked up towards a drier activity area inland.
• This is evidence that people were living on the western edge of the Cordilleran Ice Sheet at the end of the last ice age, adding to growing evidence that early peoples travelled along this coast.
• The authors note a limitation: some dates in the layer over the tracks are outliers, because that layer was disturbed.
• Footprints are probably part of many archaeological sites but are missed because they are so easily lost. The authors stopped digging so the remaining tracks stay undisturbed for future researchers with better methods.

4. How tracking was or was not used

The whole study rests on tracks and signs identification of human footprints. The authors identified the tracks as human from the arch, the toes, the offset heel and the displacement rims. They ruled out bears, whose hind paw tracks are the only local large-mammal tracks resembling human ones: the prints had a clear arch, no claw marks, were not triangular, had the first or second toe longest rather than the third, and were narrower than bear tracks. No bear front tracks were found either. They also interpreted track size (number of people), toe drag marks (barefoot or shod), heel slippage, side-by-side left and right prints (standing still), and track direction. They used standard terms for track layers: true track, undertrack, overtrack, track surface and displacement rim. No trailing was done.

5. Tracker or observer certification

Reported but not validated. The field crew are described as “very familiar with bear footprints”, which they watch for to keep workers safe, but no tracking qualification or test of their skill is reported.

6. Other technologies, skills or innovations

• Digital enhancement of track photographs with the DStretch plugin for ImageJ (free software) made faint toes, heels and rims easier to see.
• Radiocarbon dating of wood and charcoal (accelerator mass spectrometry, University of California, Irvine).
• Microscope study of sediments, pollen, diatoms and other microfossils, and identification of wood from its cells.
• Targeting dig sites by a local sea level history.
• One track (#4) was lifted out on a block of sediment (pedestalled) and taken to the laboratory.

7. Implications for conservation (from the paper)

• The authors stopped excavating so the remaining tracks stay in place for future study with better methods.
• Tracks are probably present at many archaeological sites but are missed or not recognized because they are so short-lived.