We suggest a likely age of this trackway to MIS 5c/~90 ka. We note that OSL dating is required to resolve the chronology of the site. The analysis of geological samples in thin section showed that the cement is blocky- to drusy calcite spar. This is interpreted to suggest diagenesis in the vadose zone43,44, through percolation of meteoric water which led to dissolution of calcium carbonate components of the sediment. The presence of one generation of calcium carbonate cement in these deposits (blocky calcite spar, Fig. 6b,f), which is indicative of cementation in the meteoric vadose zone, suggests that these deposits have not been re-submerged since deposition and lithification. There is no subsequent marine influence, and transmitted light petrography suggested that ~30% of the pores are unfilled. This is consistent with the overall situation recorded for the Cape south coast during the Pleistocene from existing literature21,28,45 and the modern coast-parallel wind regime46, with east to southeast winds dominant in the summer, and stronger winds from the westerly quadrant prevailing in the winter.

A further argument for the preferred younger age, is that at 90 ka the coastline was ~2 km distant11,47,48,49, compared to the MIS 5e shoreline which was at a point in excess of 6 m above present sea level27,29,33. At the time of MIS 5e, the level of the cliff containing the trackways (presently ~3 m above Mean Sea Level) would have been submerged by high sea levels.

Local29,34,50 and global51 studies have shown that during the Late Pleistocene, sea level did not reach the elevation of MIS 5e, nor did it near this elevation. The Holocene Highstand52,53 was likely associated with a 2–3 m higher-than-present sea level, but based on carbonate diagenesis its influence was not evident in the rock record at our study site. From MIS 5e, sea level retreated towards MIS 5c (which is the depositional age suggested here) with an associated shoreline ~ 2 km distant, when considering the local offshore bathymetry48. During MIS 5c, sea level was retreating and coastal dunes were likely to be migrating onto the now submerged coastal plain.

Tuttle’s criteria17 are met at the tracksite we describe, with the sole exception that the best preserved tracks exhibit three lateral digits, not four (e.g. Fig. 7a,b). This difference, we contend, is a function of preservation, not trackmaker anatomy.

The nine tracks on the northern surface that contain digital impressions were made by bipedal humans. The preservation of high definition features such as digital impressions suggests a relatively firm, possibly damp substrate, and rapid infilling of the track-bearing surface. The tracks on the southern surface do not unequivocally exhibit digit impressions. When viewed in isolation these approximate a hominin footprint morphology, but lack some of the more diagnostic hominin footprint characteristics to allow unequivocal identification. However, their occurrence in the same bedding plane, and with similar downslope bearing as the tracks on the northern surface (in some cases probably forming extensions of those trackways) strongly suggests a hominin origin, evidently from the same group of individuals or perhaps others in the group. This is likely an example of the influence of a change in the condition of the substrate from the northern surface to the southern surface on this bedding plane. Increased erosion of tracks nearer the cave mouth may also be a factor in downgrading track preservation.

The tracks seen in sagittal section in the east wall of the cave have a pace length and outline consistent with hominin tracks, and have a similar orientation as the other hominin tracks. Unequivocal confirmation of their hominin origin could be obtained by future excavation of the surrounding rock layers to reveal these natural casts in situ. The limited information that can be obtained for the tracks on the lower layer suggests a morphology intermediate between the tracks of the northern and southern surfaces of the main track-bearing layer.

The occurrence of tracks in both lateral walls of the cave, and at the junctions of the ceiling with both lateral walls and with the inner (north) wall, suggests that more tracks and trackways could easily be exposed. These tracks may be preserved with superior detail compared with those currently visible, many of which are partially eroded. Ideally the area between the northern and southern surfaces of the main track-bearing layer could be exposed, to yield one continuous track-bearing surface.

The most obvious trackway feature is the right-left sequence of large tracks. The pace length between tracks 4 and 8 is 85 cm. Track 11 is a poorly preserved right track. It probably represents a third track in this trackway, although it is not perfectly aligned with track 4 and track 8. The putative pace length between track 8 and track 11 is 66 cm. The distance between track 8 and the edge of the surface is 105 cm. Either way, a short-long (variable or alternating) gait pattern is evident. Such a gait may be employed when moving fast down a dune slope while heel planting, thereby aiding stability.

Another inferred hominin trackway is evident in the east wall of the cave (tracks 28 A, 28, 29, 30). The measured distances between these tracks, which appear in sagittal section, are 160 cm, 144 cm, 73 cm. The edge of a further track midway between tracks 28 and 29 is possibly present, yielding further pace lengths of 72 cm and 72 cm. If this is indeed a trackway, then these measurements indicate a different and more consistent gait pattern with a stride length of 144–160 cm and a pace length where measurable of 72–73 cm. These tracks also exhibit deep heel impressions, and are of similar length to many of the tracks seen on the northern surface. If an inferred pace length of ~73 cm is used, a number of plausible trackways become apparent on the northern surface, and some of these could extend into the tracks on the southern surface. However, this inference remains speculative, and until a larger track surface is exposed various interpretations are possible. Nonetheless, noting the strongly unimodal orientation, our interpretation is that there were probably multiple trackmakers. Other explanations for a unimodal orientation include repeat visits with similar bearing within a short time interval, and landscape constraints (although such constraints are improbable on dune surfaces).

Detailed analysis of human track morphology comes from Holocene tracks on level surfaces in the Namib Desert54 and from studies on habitually barefoot subjects on level surfaces in Kenya55. However, the applicability of these studies in analysing the gaits of individuals who made tracks on the downslope of a 20° dune surface is likely limited. Research on characteristic track and gait features of humans travelling down dune slopes would aid in the interpretation of the site.

Inferences have been made on human foot morphology from hominin tracksites14,55, and human behaviour, including that of groups56. Some of these inferences have been disputed15. A morpho-classificatory and morphometric approach, of the kind applied by Citton et al.57, in the Grotta della Basura tracksite in Italy, may be useful at the site we describe here, in order to estimate the number of trackmakers. Such studies would best be performed once further tracks have been exposed.

The limitations and complexities of estimating stature, velocity, mass and other measurements from track data have been described by Bennett and Morse14. Stature inferences from footprint dimensions were made by Roberts19 for the Nahoon and Langebaan tracks, using a formula (footprint length ×6.67) derived from global mean data of Mietto et al.58. Roberts thereby derived height estimates of 128.06 cm for the Nahoon trackmaker and 152.07 cm for the Langebaan trackmaker. Applying this formula to the tracks we describe here yields estimates of 153.4 cm for the largest tracks and ~116 cm for the smaller tracks.

Roberts19 noted a short pace length for the Nahoon and Langebaan trackways, and concluded that this probably was related to the difficulty of negotiating sloping and unstable surfaces. He noted a pace length of 33.04 cm for the Nahoon tracks, where the slope of the dune face was estimated at ~17°, and of 50 cm for the Langebaan tracks, where the slope of the dune face was estimated at ~15°. The pace lengths we describe of 75 cm, 85 cm, and possibly greater than 105 cm, on a dune slope of equivalent or slightly greater angle, imply a more rapid trackmaker velocity, and may be consistent with a running gait. In our view, sufficient information is not yet available to yield a velocity estimate.

Dating studies above and below the hominin track horizon would allow this site to be placed with greater certainty within the context of the hominin track record, and its temporal relationship with the other southern African Pleistocene sites to be determined. We used an approach to reach a ~90 ka age estimate for the hominin tracks which considered carbonate diagenesis and a careful comparison with known sites in the area.

Placed in a global context, unusual features of the tracksite we describe include:

occurrence in aeolianites (shared by the Nahoon and Langebaan sites)

deep heel impressions and downslope sediment rims

tracks made on an angled slope (shared with, inter alia , the Roccamonfina Volcano, Nahoon and Langebaan sites)

unimodal orientation

natural cast tracks (shared with the Nahoon site)

confined space in a small cave, with tracks on a ceiling creating documentation challenges.

The Nahoon and Langebaan Pleistocene hominin tracksites proved the potential for coastal aeolianites to preserve such features. However, when compared with other hominin tracksites, they have been described as being poorly preserved13. Bennett and Morse14 note that some authorities have questioned the human origin of the Langebaan tracks, while acknowledging that it remains the most likely interpretation. Nonetheless these sites have been regarded as important in the record of hominin ichnology, as they filled a substantial gap in the hominin track record.

Uncertainty about the age of the Engare Sero site in Tanzania appears to have been resolved, and a date of ~19 ka has been reported59. If the attribution to Homo neanderthalensis of the Vârtop Cave tracksite is accepted60, then without the South African sites there are no tracksites that can be attributed to Homo sapiens before 46 ka. However, the attribution of the Langebaan and Nahoon tracks to Homo sapiens predated the identification of Homo naledi as a Pleistocene inhabitant of southern Africa. Until reliable criteria are developed to distinguish Homo naledi tracks from Homo sapiens tracks, we contend that both should be considered as plausible or at least possible trackmakers at Late Pleistocene hominin tracksites in southern Africa. However, Homo naledi has a limited reported spatial distribution (more than 1000 km from the site we describe) and a limited temporal distribution, with an estimated minimum age of 236 ka26. It therefore seems reasonable to consider Homo sapiens as an increasingly more probable trackmaker with progressively younger tracksites such as the site we describe on the Cape south coast.

The only three known hominin tracksites from the age in which cognitively modern humans emerged are from southern Africa. When compared with the frequency of occurrence of other tetrapod track morphotypes, the frequency of hominin track occurrences may reflect population density, or at least frequency of activity in coastal dune settings.

Full documentation of aeolianite tracks would require sub-marine studies, as most of the suitable deposits are currently under water on the continental shelf. Globally, coastal aeolianites occur mostly between latitudes 20° and 40°, predominantly in the southern hemisphere along the coast of Australia and the southern and eastern coast of South Africa40.