Laetoli is a pre-historic site located in Enduleni ward of

Ngorongoro District Ngorongoro District (''Wilaya ya Ngorongoro'', in Swahili language, Swahili) is one of seven Districts of Tanzania, districts in western Arusha Region of Tanzania. The district is bordered to the north by Kenya, to the east by Monduli District, t ...

Arusha Region Arusha Region () is one of Tanzania's 31 administrative Regions of Tanzania, regions and is located in the northeast of the country. The region's capital and largest city is the city of Arusha. The region is bordered by Kajiado County and Narok C ...

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

. The site is dated to the

Plio-Pleistocene The Plio-Pleistocene is an informally described geological pseudo-period, which begins about 5 million years ago (Mya) and, drawing forward, combines the time ranges of the formally defined Pliocene and Pleistocene epochs—marking from about 5&n ...

and famous for its

Hominina The australopithecines (), formally Australopithecina or Hominina, are generally any species in the related genera of ''Australopithecus'' and ''Paranthropus''. It may also include members of ''Kenyanthropus'', ''Ardipithecus'', and '' Praeanth ...

footprint Footprints are the impressions or images left behind by a person walking or running. Hoofprints and pawprints are those left by animals with hooves or paws rather than feet, while "shoeprints" is the specific term for prints made by shoes. The ...

s, preserved in

volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...

. The site of the Laetoli footprints (Site G) is located 45 km south of

Olduvai gorge The Olduvai Gorge or Oldupai Gorge in Tanzania is one of the most important paleoanthropology, paleoanthropological localities in the world; the many sites exposed by the gorge have proven invaluable in furthering understanding of early human evo ...

. The location and tracks were discovered by archaeologist

Mary Leakey Mary Douglas Leakey, Fellow of the British Academy, FBA (née Nicol, 6 February 1913 – 9 December 1996) was a British paleoanthropologist who discovered the first fossilised ''Proconsul (mammal), Proconsul'' skull, an extinct ape which is now ...

and her team in 1976, and were excavated by 1978. Based on analysis of the footfall impressions "The Laetoli Footprints" provided convincing evidence for the theory of bipedalism in

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58National Museum of Tanzania and Terry Harrison of

New York University New York University (NYU) is a private university, private research university in New York City, New York, United States. Chartered in 1831 by the New York State Legislature, NYU was founded in 1832 by Albert Gallatin as a Nondenominational ...

, leading to the recovery of more than a dozen new Hominina finds, as well as a comprehensive reconstruction of the

paleoecology Paleoecology (also spelled palaeoecology) is the study of interactions between organisms and/or interactions between organisms and their environments across geologic timescales. As a discipline, paleoecology interacts with, depends on and informs ...

. The site is a registered National Historic Sites of Tanzania. Dated to 3.7 million years ago, they were the oldest known evidence of hominin bipedalism at that time. Subsequently, older '' Ardipithecus ramidus'' fossils were found with features that suggest bipedalism. With the footprints there were other discoveries excavated at Laetoli including Hominina and animal skeletal remains. Analysis of the footprints and skeletal structure showed clear evidence that bipedalism preceded enlarged brains in Hominina. At a species level, the identity of the Hominina who made the trace is difficult to construe precisely; ''

Australopithecus afarensis ''Australopithecus afarensis'' is an extinct species of australopithecine which lived from about 3.9–2.9 million years ago (mya) in the Pliocene of East Africa. The first fossils were discovered in the 1930s, but major fossil finds would not ta ...

'' is the species most commonly proposed.

Background

History of research

Earliest known human footprints - one set - australopithecus afarensis - Smithsonian Museum of Natural History - 2012-05-17

Laetoli was first recognized by western science in 1935 through a man named Sanimu, who persuaded archeologist

Louis Leakey Louis Seymour Bazett Leakey (7 August 1903 – 1 October 1972) was a Kenyan-British palaeoanthropologist and archaeologist whose work was important in demonstrating that humans evolved in Africa, particularly through discoveries made at Olduvai ...

to investigate the area. Several mammalian fossils were collected with a left lower canine tooth originally identified as that of a non-human primate, but later was revealed (in 1979, by P. Andrews and T. White) as the site's first fossil

hominin The Hominini (hominins) form a taxonomic tribe of the subfamily Homininae (hominines). They comprise two extant genera: ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos), and in standard usage exclude the genus '' Gorilla'' ( gorillas) ...

. In 1938 and 1939, German archaeologist

Ludwig Kohl-Larsen Ludwig Kohl-Larsen (born ''Ludwig Kohl''; 5 April 1884 in Landau in der Pfalz – 12 November 1969 in Bodensee) was a German physician, amateur anthropologist, and explorer. Biography In 1911, he traveled as ship's doctor with Wilhelm Filchn ...

studied the site extensively. Several hominin remains, including premolars, molars, and incisors, were identified. A later excavation in 1959 revealed no new hominins, and Laetoli went relatively unexplored until 1974—when the discovery of a hominin premolar by George Dove revived interest in the site.

returned and almost immediately discovered the well-preserved remains of hominins. In 1978, Leakey's 1976 discovery of hominin tracks—"The Laetoli Footprints"—provided convincing evidence of bipedalism in Pliocene hominins and gained significant recognition by both scientists and laymen.

Possible tracemaker

Although much debated, researchers have tentatively concluded that ''

'' is the species of the three hominins who made the footprints at Laetoli. This conclusion is based on the reconstruction of the foot skeleton of a female ''A. afarensis'' hominin by anthropologists Tim D. White and Gen Suwa of the University of California, as well as detailed footprint analysis by Russel Tuttle of the University of Chicago; he compared human and other bipedal animals such as bears and primates, including gaits and foot structure, and taking into account the use of footwear. For gait Tuttle looked at the step length, stride length, stride width, and foot angle, and determined that ''A. afarensis'' was more human-like in gait than ape-like. ''A. afarensis'' is an obligate bipedal hominin with the beginnings of

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

attributed to its species, and brain size very similar to that of modern

chimpanzee The chimpanzee (; ''Pan troglodytes''), also simply known as the chimp, is a species of Hominidae, great ape native to the forests and savannahs of tropical Africa. It has four confirmed subspecies and a fifth proposed one. When its close rel ...

s and

gorilla Gorillas are primarily herbivorous, terrestrial great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four or five su ...

s. Analysis of the Laetoli footprints indicated the characteristics of obligate bipedalism: pronounced heel strike from deep impressions, lateral transmission of force from the heel to the base of the lateral

metatarsal The metatarsal bones or metatarsus (: metatarsi) are a group of five long bones in the midfoot, located between the tarsal bones (which form the heel and the ankle) and the phalanges ( toes). Lacking individual names, the metatarsal bones are ...

, a well-developed medial longitudinal arch, adducted big toe, and a deep impression for the big toe commensurate with toe-off.

Age and dating techniques

Two dating techniques were used to arrive at the approximate age of the beds that make up the ground layers at Laetoli: potassium-argon dating and analysis of

stratigraphy Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithost ...

. Based on these methods, the layers have been named as follows, starting with the deepest: Lower Laetolil Beds, Upper Laetolil Beds, Lower Ndolanya Beds, Upper Ndolanya Beds, Ogol lavas, Naibadad Beds, Olpiro Beds, and Ngaloba Beds; it is the ancient Laetolil Beds that contain the footprints trackway. The upper unit of the Laetolil Beds dated back 3.6 to 3.8 million years ago. The beds are dominantly tuffs and have a maximum thickness of 130 meters. No mammalian fauna were found in the lower unit of the Laetolil Beds, and no date could be assigned to this layer. The Ndolanya Beds, which are located above the Laetolil Beds and underlie the Ogol lavas, are clearly divisible into upper and lower units separated by a widespread deposit of

calcrete Caliche () is a soil accumulation of soluble calcium carbonate at depth, where it precipitates and binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or s ...

up to one meter thick. However, like the Lower Laetolil Beds, no date can be assigned to the Ndolanya Beds. The Ogol lavas date back 2.4 million years. No fauna or artifacts are known from the Naibadad Beds, but they are correlated with a bed layer at Olduvai Gorge based on mineral content. Pleistocene fauna and Acheulean artifacts have been found in the Olpiro Beds. Based on a trachytic tuff which occurs within the beds, the Ngaloba Beds may therefore be dated between 120,000 and 150,000 years BP.

Discoveries

Hominina footprints from site G

The principal discovery, made by Mary Leakey and her team in 1976 (and fully excavated by 1978), is a 75-foot (24-meter) line of

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

footprints, preserved in powdery

originally thought to have been from an eruption of the nearby (20 km) Sadiman volcano. However, recent study of the Sadiman volcano has shown that it is not a source for the Laetoli Footprints Tuff (Zaitsev ''et al.'' 2011). Soft rain cemented the ash-layer (15 cm thick) to

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...

without destroying the prints. In time, they were covered by other ash deposits. The fossil footprints were rather whimsically discovered by Yale's Andrew Hill when visiting Mary Leakey in 1976. While walking back to camp one evening, Hill fell trying to avoid a large ball of elephant dung thrown at him by a colleague. With his face only inches from the rock, he recognized footprints made by antelopes and rhinos preserved in the volcanic ash, and among these, hominid footprints. The Hominina prints were produced by three individuals, one walking in the footprints of the other, making the preceding footprints difficult to recover. As the tracks lead in the same direction, they might have been produced by a group visiting a waterhole together, but there is nothing—or very little (see below, Interpretation and significance)—to support the common assumption of a

nuclear family A nuclear family (also known as an elementary family, atomic family, or conjugal family) is a term for a family group consisting of parents and their children (one or more), typically living in one home residence. It is in contrast to a single ...

. Roberto Sáez claims that this 27-metre trail of about 70 footprints was left by two ''Australopithecus'' walking in front, while the third hominid walked behind, superimposing its steps on the footprints left by one of the two in front. He acknowledges that it will never be possible to prove that this is true. The

s demonstrate that the Hominina habitually walked upright as there are no knuckle-impressions. The feet do not have the mobile big toe of apes; instead, they have an arch (the bending of the sole of the foot) typical of modern humans. The hominins seem to have moved in a leisurely stroll. Computer simulations based on information from ''A. afarensis'' fossil skeletons and the spacing of the footprints indicate that the Hominina were walking at 1.0 m/s or above, which matches human walking speeds. The results of other studies have also supported the theory of a human-like gait.

Hominina footprints from site S

In 2015, footprints of the same age as the first reported footprints were unearthed at a site approximately 150 meters south of the original site G footprints. This site is called site S, and the 2 individuals who made the prints are named S1 and S2. S2 is represented by only 1 print, but S1 left a track of prints, the first 4 of which are shown in the composite image, along with an analysis of step and stride lengths. Further analysis indicated that individual S1 was considerably larger than any of the three individuals from site G.

Other footprints and artifacts

Other prints show the presence of twenty different animal species besides the hominin ''A. afarensis'', among them

hyena Hyenas or hyaenas ( ; from Ancient Greek , ) are feliform carnivoran mammals belonging to the family Hyaenidae (). With just four extant species (each in its own genus), it is the fifth-smallest family in the order Carnivora and one of the sma ...

s, wild cats (

Machairodus ''Machairodus'' (from , 'knife' and 'tooth') is a genus of large Machairodontinae, machairodont or ''saber-toothed cat'' that lived in Africa and Eurasia during the Middle Miocene, Middle to Late Miocene, from 12.5 million to 8.7 million years ...

baboon Baboons are primates comprising the biology, genus ''Papio'', one of the 23 genera of Old World monkeys, in the family Cercopithecidae. There are six species of baboon: the hamadryas baboon, the Guinea baboon, the olive baboon, the yellow ba ...

wild boar The wild boar (''Sus scrofa''), also known as the wild swine, common wild pig, Eurasian wild pig, or simply wild pig, is a Suidae, suid native to much of Eurasia and North Africa, and has been introduced to the Americas and Oceania. The speci ...

giraffe The giraffe is a large Fauna of Africa, African even-toed ungulate, hoofed mammal belonging to the genus ''Giraffa.'' It is the Largest mammals#Even-toed Ungulates (Artiodactyla), tallest living terrestrial animal and the largest ruminant on ...

gazelle A gazelle is one of many antelope species in the genus ''Gazella'' . There are also seven species included in two further genera; '' Eudorcas'' and '' Nanger'', which were formerly considered subgenera of ''Gazella''. A third former subgenus, ' ...

rhino A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...

s, several kinds of

antelope The term antelope refers to numerous extant or recently extinct species of the ruminant artiodactyl family Bovidae that are indigenous to most of Africa, India, the Middle East, Central Asia, and a small area of Eastern Europe. Antelopes do ...

, ''

Hipparion ''Hipparion'' is an extinct genus of three-toed, medium-sized equine belonging to the extinct tribe Hipparionini, which lived about 10-5 million years ago. While the genus formerly included most hipparionines, the genus is now more narrowly defi ...

'', buffaloes, elephant relatives (of the extinct genus ''

Deinotherium ''Deinotherium'' (from Ancient Greek , ''()'', meaning "terrible", and ''()'', meaning "beast"), is an extinct genus of large, elephant-like proboscideans that lived from the middle-Miocene until the end of the Early Pleistocene. Although its ap ...

''),

hare Hares and jackrabbits are mammals belonging to the genus ''Lepus''. They are herbivores and live Solitary animal, solitarily or in pairs. They nest in slight depressions called forms, and their young are precociality, able to fend for themselves ...

s and

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s. Rain-prints can be seen as well. Few footprints are superimposed, which indicates that they were rapidly covered up. Most of the animals are represented by

skeletal A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fram ...

remains discovered in the area. No artifacts have been found in the vicinity, at least within the ancient Laetolil Beds that contain the trackway. However, artifacts from the younger Olpiro and Ngaloba Beds, also preserved at Laetoli, have been found.Ndessokia, P. N. S., 1990. ''The Mammalian Fauna and Archaeology of the Ndolanya and Olpiro Beds, Laetoli, Tanzania.'' Ph.D. Dissertation,

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...

Interpretation and significance

Before the discovery of the Laetoli footprints, there was much debate as to which developed first in the human evolutionary time line: a larger brain or bipedalism. The discovery of these footprints settled the issue, proving that the Laetoli hominins were fully bipedal long before the evolution of the modern human brain, and were bipedal close to a million years before the earliest known stone tools were made. The footprints were classified as possibly belonging to ''Australopithecus afarensis''. Some analysts have noted in their interpretations that the smaller trail bears "telltale signs that suggest whoever left the prints was burdened on one side." This may suggest that a female was carrying an infant on her hip but this cannot be proven for certain. The footprints themselves were an unlikely discovery because they closely resemble modern human footprints, despite being almost 4 million years old. It is noted that the toe pattern is much the same as the human foot, which is much different from the feet of chimpanzees and other non-bipedal beings. The footprint impression has been interpreted as the same as the modern human stride, with the heel striking first and then a weight transfer to the ball of the foot before pushing off the toes. Based on stratigraphic analysis, the findings also provide insight into the climate at the time of the making of the footprints. Pliocene sediments show that the environment was more moist and productive than now. Climate changes that caused a shift from forest to grassland environments have a strong correlation with upright posture and bipedalism in hominins. This could have initiated the evolution to bipedalism of the hominins found at Laetoli.

Preservation and conservation

In 1979, after the Laetoli footprints were recorded, they were re-buried as a then-novel way of preservation. The site was re-vegetated by

acacia ''Acacia'', commonly known as wattles or acacias, is a genus of about of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa, South America, and Austral ...

trees, which later gave rise to fears over root growth. In mid-1992, a GCI-Tanzanian team investigated this by opening a three-by-three meter trench, which showed that roots had damaged the footprints. However, the part of the trackway unaffected by root growth showed exceptional preservation. The success of the experiment led to an increased practice in reburials for preserving excavated sites. In 1993, measures were taken to prevent erosion. The original trackway was remolded and new casts were made. As the trackway is very fragile, the new replica cast was used to guide re-excavation in the field. A team of specialists, one being Fiona Marshall, re-excavated half of the trackway to record its condition, stabilize the surface, extract dead roots and rebury it with synthetic geotextile materials. This allows the trackway surface to breathe, and protects it against root growth. Proposals for lifting the track and moving it to an enclosed site have been suggested, but the cost is viewed as outweighing the benefits: the process would require much research, a large amount of money, and there is a risk of loss or damage. Thus, burial seems to be the most effective method of preservation.

References

Bibliography

* Archaeologyinfo.com (n.d.) Australopithecus afarensis. Retrieved from http://archaeologyinfo.com/australopithecus-afarensis/ * Ditchfield, P. & Harrison, T. (2011). Sedimentology, Lithostratigraphy and Depositional History of the Laetoli Area. In T. Harrison (Ed.), Paleontology and Geology of Laetoli: Human Evolution in Context: Geology, Geochronology, Paleoecology and Paleoenvironment, Vertebrate Paelobiology and Paleoanthropology. 1, pp. 47–76, Dordrecht, Netherlands: Springer * Leakey, M.D. (1981). Discoveries at Laetoli in Northern Tanzania. Proceedings of the Geologists’ Association. 92 (2), pp. 81–86. * Tuttle, R.H., Webb, D.M., & Baksh, M. (1991). Laetoli Toes and Australopithecus afarensis. Human Evolution. 6 (3) pp. 193–200. * Tuttle, R.H. (2008). Footprint Clues in Hominid Evolution and Forensics: Lessons and Limitations. Ichnos. 15 (3-4), pp. 158–165. * White, T.D. & Suwa, G. (1987). Hominid footprints at Laetoli: Facts and Interpretations. American Journal of Physical Anthropology. 72 (4). pp. 485–514. * Zaitsev, AN, Wenzel, T, Spratt, J, Williams, TC, Strekopytov, S, Sharygin, VV, Petrov, SV, Golovina, TA, Zaitseva, EO & Markl, G. (2011). Was Sadiman volcano a source for the Laetoli Footprint Tuff? Journal of Human Evolution 61(1) pp. 121–124. *

External links

Footprints to Fill : Flat feet and doubts about makers of the Laetoli tracks
- Scientific American (August 2005)
Leakey, M. D. and Hay, R. L. - Pliocene footprints in the Laetolil Beds at Laetoli, northern Tanzania
- Nature

- PBS - Evolution

- film about

- artworks for and about Laetoli
Footprints From the Past
2009-10-31) * Sedimentology, Lithostratigraphy and Depositional History of the Laetoli Area (2011) Ditchfeld & Harrison https://doi.org/10.1007%2F978-90-481-9956-3_3 * Laetoli Toes and Australopithecus afarensis (1991) Tuttle, Webb, Baksh https://doi.org/10.1007%2FBF02438142
Discoveries at Laetoli in northern Tanzania (1981) Leakey

Hominid Footprints and Laetoli: Facts and Interpretations (1987) White, Suwa

The Laetoli Footprints (1996) Agnew, Demas, Leakey

Footprint Clues in Hominid Evolution and Forensics: Lessons and Limitations (2008) Tuttle
* Description of Australopithecus Afarensis. http://archaeologyinfo.com/australopithecus-afarensis/-Create 3 new sections: Interpretation, controversy of the footprints, and preservation and conservation problems
Human Timeline (Interactive)
– Smithsonian Institution, Smithsonian,

National Museum of Natural History The National Museum of Natural History (NMNH) is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. With 4.4 ...

(August 2016). {{National Historic Sites of Tanzania Archaeological sites in Tanzania Pliocene paleontological sites of Africa Fossil trackways Fossils of Tanzania Prehistoric Tanzania Paleoanthropological sites Pleistocene paleontological sites of Africa Archaeological sites of Eastern Africa First 100 IUGS Geological Heritage Sites