Who Made the Laetoli Footprints? A Look at the Consensus, And the Dissenters (Answers in Genesis Primarily)

3.7 million years ago a small band of hominids were making their way across Laetoli, Tanzania when they happened to have the misfortune of being caught in the aftermath of a nearby volcanic eruption. The troop was small, with two assured individuals and a potential two more, and as they lumbered across the terrain's fresh ashfall, they left deep footprints behind to catalog their journey.  The smaller tracks are identified as the female of the two and was perhaps burdened with carrying a child on her hip according to the weight distribution and the male's tracks have what appear to be juvenile tracks within them, as if a youngster was following within their parent's footsteps close behind. 

These tracks were discovered in 1976 by the venerable Mary Leakey, and at the time they were considered the first evidence of assured bipedality in a hominin. Of course, many specimens of earlier species now deemed at least primarily bipedal have now been found (such as A. ramidus and perhaps even S. tchadensis) due to their incredibly well-preserved skeletons.

Since then, Creationists of many kinds have attempted to discredit the tracks, claiming they are certainly human (or within human variability) and that the "chimp-like" A. afarensis could never have made such remarkable trace fossils. 

In the following post, we will examine the Laetoli Footprints in detail, along with the anatomical requirements for bipedality, the specimens of A. afarensis in the fossil record and the specific dissent of YEC organization Answers in Genesis. 

Shall we, my fellow hominids?

Part 1: A Basic Rundown of the Laetoli Site

The Laetoli Tracks consist of 75 foot line of foot imprints in a layer of hardened ash located in Laetoli, Tanzania. 

The tracks themselves are best preserved in the steps of the two primary individuals, whose stride appears to be 47 cm (Male) and 28 cm (Female) in length. The dimensions are 21. 5 cm long and 10 cm wide (Male) and 18.5 cm long, and 8.8 wide  (Female). As such, sexual dimorphism appears to be present in the foot size, although the stride is perhaps partially due to the female's burdened gait favoring one side. 

There are no knuckle impressions whatsoever accompanying the prints, and the feet lack a fully divergent big toe (trademark for the great apes). Furthermore, the foot arch on all visible tracks is nearly akin to a modern human, and thus also all of genus homo. 

Even back in the 70's these tracks were tentatively attributed to Australopithecus afarensis by Mary Leaky and her team, as the most complete specimen (nicknamed "Lucy") had only just been discovered and the initial analysis seemed to support the tracks had been made around the time that Lucy had died.  

This was further supported by an analysis of nearby fauna tracks also made in the ash, which included those of Hipparion (a three-toed basal equid) and Deinotherium, whose remains had been found in the vicinity of Lucy Northward. 

Now, we can certainly make arguments that radiometric dating confirms (to a near-definitive point) that these tracks were made by the most common hominin in the area at the time: A. afarensis. This will be commonly ignored by Young Earth Creationists though, as they do not trust the nature of radiometric dating and find teh tracks to be "too human" to be attributed to what they consider a "pure ape". 

For this reason, we will stick exclusively to analyzing the anatomy of A. afarensis and the physical characteristics of the tracks in order to answer two very important questions: 

1: Could the tracks have been mechanically produced by a modern human? 
2: If not, could Australopithecus afarensis have made them?

We already know the local fauna support that A. afarensis made these tracks, but typically this is also not good enough for YECs as they propose all animals (including humans) lived at one time prior to the Global Flood. This means it is of no consequence to them that Hipparion was milling about alongside these tracks. 

So let us instead move to look at conventional anthropology's Person of Interest in depth.

Part 2:  The Art of Bipedalism

Bipedality is a tricky game. As far as locomotion goes, the safer bet is certainly to distribute weight on four available limbs rather than balancing on two. However, for an organism with forelimbs that can serve a more versatile purpose it is a worthy trade. 

All modern birds locomote on two hind legs. This frees up the wings for flight, thermoregulation, water propulsion, sexual display and defense. 

In more basal primates, while forelimbs may be used to move about quadrepedally through the trees or bear weight on the knuckles terrestrially, they also serve to strengthen social bonds through grooming and manipulate objects and materials for nest building or even tool use. 

But in the hominids our free arms allow us to move and use tools at the same time, as well as carry our belongings around or bring food back to a home base. 

Furthermore, standing on our hind limbs gives us an incredible vantage point to spot both our predators and our prey. 

But what actually makes a primate a biped? What anatomically must be present in order to move about on two back limbs in an efficient and "worthwhile" manner? 

There are generally four big skeletal changes that must occur before muscle attachments can maximize efficiency. Your basic primate biped MUST have some degree of the following:

1. Location of the foremen magnum opening in the skull
2. Valgus knee presence, or the “carrying angle”
3. Halux (big toe) is in-line with the rest of the toes
4. Pelvic structure

Location of the Foremen Magnum: The foremen magnum is the opening at the base of the skull that allows the spinal cord to pass from the brain to the rest of the body. In bipedal animals such as humans or birds, the foremen magnum is directly ventral, or underneath, the skull. In animals that are primarily or partially quadrupedal, the opening is more dorsal.
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Australopithecus afarensis is directly intermediate from a chimpanzee and a human, the former of which are habitual bipeds and the latter of which are obligate bipeds. (pictured below is the Dikika Child, ventral view)

 The Valgus Knee, or "Carrying Angle": The valgus knee is responsible for placing the maximum center of gravity below the body directly in order to make locomotion efficient. This also reduces the body surface area exposed to direct sunlight, potentially having thermoregulation benefits. Humans and all hominids we have record of, including the most primitive Sahelanthropus tchadensis, possess this knee. 

Pictured below to the Left: A. afarensis knee (patella missing), Right: Human knee

Hallux (big toe) in-line with rest of toes: The hallux is vital for human push off and balance when we walk. In chimpanzees, they cannot walk bipedally for long periods in part due to their inefficient movement thanks to awkward push offs. A. afarensis has a foot and toe structure FAR more in line with modern humans than chimps. Specimens of Australopithecus Feet Below: Left and Below: Dikika Child,  Right: Lucy,  Above: Little Foot

Hip Structure: Flared blades indicates attachment sites for muscle that are similar to that of genus homo, more so than that of the great apes. Bowl-Shape allows for a strong pelvic floor, absolutely necessary for bipedal walking. 

To summarize quite simply: all the requirements that are necessary for modern humans to remain upright and walk are ALSO found on A. afarensis, albeit to "less efficient" degrees. 

What this says definitively is this: Australopithecus afarensis certainly COULD HAVE made those prints based on it's ability to walk upright, and general foot shape. But now we must ask our first question once more: 

Could a human have made the Laetoli footprints, mechanically speaking? 

If so, the Laetoli Footprints are inconsequential to Young Earth Creationists. A human could have made them, and the connections the prints have to a nearby hominid don't really matter. 

But, if not, then we have a new issue. We have an animal that made prints so close to that of modern humans it fooled an entire denomination. We have an animal, that from the waist down, is very nearly a member of our genus. But from her beltline up, she is a "Pure Ape", from her prognathism, canines and browridge to her abysmal braincase. 

We have the "ape-man" (or "ape-woman" in Lucy's case) that Answers in Genesis is always crowing for. 

Fortunately, a very curious bunch decided to test the dimensions, gait, stride and weight distribution of the tracks against those of both modern humans and chimpanzees (common). 

So, what did THEY find?

Part 3: The Royal Society and the Laetoli Footprints

This portion will contain quite a bit of pasted material from the paper, which was published in 2016, and can be found here.

The title says it all: "Laetoli footprints reveal bipedal gait biomechanics different from those of modern humans and chimpanzees"

The experiment gathered data on modern human locomotion, chimpanzee locomotion and the Laetoli footprints. They then compared the data sets. 

The methods are as follows: 

Human Collection (performed in soil closest in grain size to the Laetoli Ashfall)

"The experiments that produced the human comparative dataset were conducted in the field at Ileret, Kenya, with 41 habitually barefoot and minimally shod modern humans (15 adult males, 14 adult females, 10 juvenile males, 2 juvenile females) producing a total of 490 footprints, of which 245 were used in this analysis (see below)...I n each trial, videos were recorded in a lateral view, and these were later digitized for two-dimensional kinematic analysis. The footprints produced in each trial were photographed, with scale, from a variety of angles and orientations such that high-resolution, scaled three-dimensional models could be rendered using photogrammetry software"

Chimpanzee Collection

"A set of experiments analogous to the human footprint experiments were performed with two chimpanzees in the Primate Locomotion Laboratory at Stony Brook University, in accordance with the policies of the Stony Brook University Institutional Animal Care and Use Committee. Chimpanzees were trained through positive reinforcement to walk bipedally at their preferred speeds across a trackway containing a sample of the same sediment used in the human experiments. Substrate conditions (compaction and hydration levels) were adjusted such that the chimpanzees produced footprints of similar depths to those created in the human experiments, which were in turn similar to the Laetoli prints."

Laetoli Collection (Superimposed Prints from G2 trackway excluded)

"Because the Laetoli hominin footprints remain buried for conservation purposes, all data were collected from first-generation casts prepared during the site's initial excavation [25] and currently stored at the National Museums of Kenya. Casts of every footprint were not available, but they were available for many of the better-preserved prints from the southern portions of the footprint trackways [26]. The morphology of each was quantified following the same procedure as for the experimentally produced footprints."

Analysis (in depth and figures can be found in paper) and Conclusion

“The Laetoli footprints, which are morphologically distinct from those of modern humans (figure 2), show lower bgPC scores than the footprints of modern humans (figure 3b), and therefore point to a bipedal gait that involved a more flexed lower limb posture at foot strike than is typically observed in modern humans. This direct evidence of a bipedal gait that involved relatively more flexed lower limbs concurs with certain inferences derived from Australopithecus skeletal fossils...
In sum, the functional implications of the Laetoli tracks are consistent with previous interpretations of distinctive anatomy in Australopithecus and provide an emerging picture, based on direct records of locomotor behaviour, of a form of bipedalism in early hominins that differed from that of modern humans. We acknowledge that there are limitations to the conclusions that can be drawn from our experimental approach (electronic supplementary material, note S3). But, based on our data, it appears that relative to the specific pattern of gait seen in modern humans today, the Laetoli footprints show evidence of a distinct gait that involved relatively greater limb flexion at touchdown and potentially a less arched foot. These differences were almost certainly not as dramatic as those that distinguish the bipedal gaits of modern humans and modern chimpanzees, but nonetheless they may have had critical wide-ranging effects on the palaeobiology of the Laetoli hominins.
Ultimately, these results support the hypothesis that the evolution of hominin bipedalism was a process [47] during which slightly but significantly different gait kinematics, kinetics and morphology evolved in different hominin taxa. Regardless of the environmental and evolutionary circumstances that may have surrounded the Laetoli trackmakers, direct evidence from the Laetoli footprints suggests that the Pliocene hominins at Laetoli (probably but not certainly A. afarensis) employed a form of bipedalism that was well developed but not equivalent to that seen in modern humans today. While the post-cranial anatomy required for a well-developed bipedal gait may have emerged at an earlier date and persisted for a long time [7], it remains to be seen when, how and why the specific biomechanics of modern human bipedalism evolved."

The consensus then is fairly clear: The Laetoli footprints are markedly NOT human in their physicality. They are similar in gait, but distinct in nearly every other way from the prints made by modern H. sapiens. 

As such, we reach the following conclusion: The Laetoli footprints were definitively made by an Australopithecine and not a member of Genus Homo. This is confirmed by radiometric dating, stratigraphy, anatomy of various members of the Hominin and Hominid clades, and biomechanics of the physical tracks n comparisson to said clade members. 

Below are two sets of prints, the left is A. afarensis and the right is an Aboriginal Human 

Part 4: So what does Answers in Genesis have to say About all This? 

Not a whole lot, honestly. In "A Look at Lucy's Legacy" the famous "no dinosaurs have feathers" Dr. Menton leads an article concerning some of Lucy's Traits. This is important specifically because by denying A. afarensis's bipedality AiG seems to suggest humans are the only viable candidate for the Laetoli prints (as if all the rest of the australopiths and genus homo aren't in the picture at all.) 

Curiously, the latest news I could find on Aig concerning Laetoli WAS this article on Lucy. The last Laetoli-specific piece seems to have been in 2011 "Laetoli Revisited" or something along those lines.

Here are some quotes from the linked "Lucy" article, as well as some rebuttals. 

• On the Footprints

“Paleoanthropologist Timothy White, who has worked with both Leakey and Johanson, attests to the obviously human appearance of the Laetoli prints. “Make no mistake about it, they are like modern human footprints,” he explains. “There is a well shaped modern heel with a strong arch and good ball of the foot in front of it. The big toe is straight in line. It doesn't stick out to the side like an ape toe.”11 White, who—unlike Mary Leakey—did associate the Laetoli prints with Lucy, also commented on the human-like gait the prints depict. He said, “I don’t mean to say that there may not have been some slight differences in the foot bones; that’s to be expected. But to all intents and purposes, those Laetoli hominids walked like you and me, and not in a shuffling run, as so many people have claimed for so long.”

Precisely, although it was also these expert anatomists who categorized the DIFFERENCES that the gait and prints had in comparison to true sapiens tracks: the in-line but diagonal big toe, weight distribution unlike both chimps and humans and most importantly the posture the prints implies.

“Yet because radiometric dating of the volcanic tuffs in which the footprints were made points to a 3.66 million year date for them,13 evolutionists maintain these prints cannot be human, no matter what they look like (because humans had not yet evolved).”

That’s not correct though, the reason the Laetoli tracks aren’t human is for the reasons mentioned above. Modern technology allows us to actually empirically compare things like topography as well, and as in the linked study above, this ALSO confirms the identity of the trackmakers as decidedly not human.

• "More controversy"

 
“The first bit of evidence that convinced Johanson he had found a Hadar hominid back in 1973, the valgus (slightly knock-kneed) angle of the knee, is actually present in some apes, notably the orangutan and the spider monkey. Therefore, the angle of the knee is not diagnostic of bipedality, despite Johanson’s confidence that he had found a new hominid. But the diagnosis of bipedality rests on more evidence, including the australopithecine pelvis and the suggestion of a lumbar curve in some reconstructions.”

The knee seen in orangutans is no where near the degree that we see in the hominids. It is a TYPE, but it is not actually conducive to bipedality especially in conjunction with the animal’s other traits. The knees of arboreal "clamberers" is more bow-legged than that seen in the australopithecines in order to amble using four limbs. It gives them a flexability not seen in the more terrestrial Great Apes! 

As for spider monkeys, the same is true. It is a localized adaption that looks nothing like the degree of femoral angling we see in the hominins. 

“in the Journal of Human Evolution, offer a different reconstruction allowing for a unique sort of locomotion. Berge writes, “The results clearly indicate that australopithecine bipedalism differs from that of humans. (1) The extended lower limb of australopithecines would have lacked stabilization during walking; and (2) the lower limb would have shown greater freedom for motion, which can be interpreted as the retention of a partly arboreal behavior.”

This is accurate and is precisely what we (and Darwin) expected to find. Going overnight to efficient bipedality would falsify evolutionary theory entirely.

• "Handy anatomy"

“Lucy’s bones show the features used to lock the wrist for secure knuckle-walking seen in modern knuckle-walkers.”


Yes, again, this is expected. There would be no immediate pressure to actually lose this trait, especially considering although AiG proposes the primary reason hominids evolved bipedality was to free the hands, this is not so. This was a convenient side effect. The true reason is unknown, although many ideas exist. Much is there to support the climatographical approach that the climate’s change to savanna would have favored being able to view over the grasses for predators, and pressured (to some degree) the exodus from the trees. 
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Part 5: Conclusion TL;DR

Despite numerous attempts by Answers in Genesis to debunk the Laetoli footprints as nothing more than human tracks (and by proxy, attempts to debunk australopithecine bipedality) they fail on nearly every level and are forced to show what little knowledge about evolution they actually have. 

The nature of the Laetoli Footprints being decidedly non-human and VERY indicative of the local australopithecine population of the time is well understood by anthropologists and anatomists alike. Experiments have been repeatedly performed to compare biomechanics and have independently reached this conclusion. 

As such, the fact that Answers in Genesis has not released a commentary on the latest 2016 findings is telling and does not bode well for their case that the prints are those of an anatomically modern human. 

I suspect the next angle will be something along the lines of "So what if it's a bipedal ape. That doesn't mean we evolved from it!" 

And the question then becomes: where does one draw the line then? At the apes that walk? The apes that think? The apes that use tools? 

All of these categories describe not only us, but the australopithecines too. Because there is no physical means by which to separate humans from apes, any more than one could separate dogs from canids.