AFRICA, THE CRADLE OF MANKIND

 Historical Aspects of Human Evolution Studies

In the previous post (In search for the missing link) we saw how following Darwin's idea  of common ancestor and the role of fossils in providing evidence of evolution  the scientific community embarked upon in search of the missing link. This led to the discovery of fossil humans in many parts of  Asia and Europe, but the missing link remained elusive. In this post we shall learn how the discovery of fossil humans brought Africa to the limelight, as the cradle of mankind. 

Africa, the Cradle of Mankind

A fossil discovery in 1921  marks the recovery of the first in a very long line of non-modern humans from the African continent. A skull (Rhodesian Man) was recovered during the course  of mining operations at a place called Broken Hill in Northern Rhodesia (now Kabwe, Zambia). During 1921–1925, further fossil human remains  were found; extinct fauna and Middle Stone Age lithics also were recovered from the same site (Balzeau et al, 2017). 

Just  three years later, in 1924, the skull of  a 3-year-old child was discovered in a limestone quarry near Taung, South Africa. It was among the first early human fossils to be found in Africa -- and the first early human fossil discovery to draw major attention to this region as a place of origin of the human family tree (Taung Child, www.si.edu). The Taung Child’s fossilised anatomy for the  first time presented evidence of an upright, two-legged (bipedal) walking  early human. 

In 1925, University of Witwatersrand anatomist Raymond Dart, published a paper describing the fossil skull of the  juvenile “half-ape, half-human”.  Dart identified certain features of the face, the teeth, the cranium (skull cap), and the brain  that foreshadowed those of Homo sapiens and made the startling claim that what was essentially a bipedal ape signalled the beginning of the human lineage separate from the African great apes.  Dart called it Australopithecus africanus, the southern ape of Africa, and asserted that it  provided clear evidence that Africa had been the cradle of mankind (Dart, 1925). 

Dart's child from Taung, presented as the "missing link" from Africa, met a chilly reception in Europe. The authorities dismissed it as, at best, a relative of the chimpanzee or gorilla with little relevance to human ancestry, stressing that until an adult specimen was available, the matter was hardly worth discussing. This attitude prevailed even though Dart took the specimen to Britain in 1931 and exhibited it at scientific gatherings (Brain, 2003).  

This was perhaps due to the near-simultaneous  discovery of significant fossil human remains from Zhoukoudian (Dragon Bone Hill) in China which quickly eclipsed whatever controversy the diminutive skull from Taung elicited. Excavation (1921-1929) at Zhoukoudian, near Beijing,  by the Canadian anatomist Davidson Black produced a vast collection of artifacts and numerous fossils belonging to a species named Sinanthropus pekinensis, popularly known as Peking Man. More new Pithecanthropus specimens were discovered in Indonesia during the 1930s (Goodrum, 2009). As was the case with Java Man, the more complete Chinese fossils fulfilled the expectations of many scientists who thought that earliest human ancestors evolved in the East. Comparative analysis of the Javanese and Chinese fossils revealed a great deal of similarity, and all of the fossils were ultimately subsumed in the species Homo erectus (Gundling, 2010). 

Although Dart endured severe criticism overseas, in South Africa he  enjoyed the unwavering support of Robert Broom, a palaeontologist, who  started a deliberate search for an adult fossil of Australopithecus. Broom’s attention was drawn  to the Sterkfontein caves near Krugersdorp, where lime mining had unearthed fossil baboon skulls as at Taung. In August 1936,  Broom was given the endocranial cast of an adult ape-man by the quarry manager and in the next few days he found much of the rest of the skull. One month later his report on Australopithecus transvaalensis, as he named the new find, appeared in Nature and The Illustrated London News (Brain, 2003). 

In 1938 Broom further described a second kind of hominid  with a wide flat face and extremely large molar teeth, Paranthropus robustus, from the nearby cave of Kromdraai.  Subsequent work has shown that this "robust" ape-man lineage arose from an africanus-like stock about 2.5 million years ago and then coexisted with early humans until about a million years ago, before becoming  extinct (Brain, 2003). Thereafter, Dart identified and described several new Australopithecus specimens from the Makapansgat Limeworks cave, 250 km northeast of Johannesburg. 

With fossils of adult ape-men now available for study, Dart's concept of Australopithecus as an African ancestor of later humans was generally accepted (Brain, 2003). 

Louis and Mary Leakey had been scouring the fossil-bearing sediments in and around eastern Africa’s Great Rift Valley for decades when on July 17, 1959, Mary discovered a very complete robust ape-man skull within the sediments dated 1.75 ma at Olduvai Gorge, Tanzania. The Leakeys called their new discovery Zinjanthropus boisei and  referred to it as “Zinj” or “Dear Boy” (Zinj is an old name for East Africa).  The press nicknamed it “Nutcracker Man” because of its huge jaws and teeth. The Leakeys’ famous fossil find is now called Paranthropus boisei or Australopithecus boisei (Broderick, 2019). This has been followed by numerous other finds in Tanzania, Kenya, Ethiopia, and elsewhere, making East Africa a hotspot of human evolution. 

Later, between 1960 and 1963, a team led by Louis and Mary Leakey recovered  the fossilised remains of a unique early human from the same layers of rock and dirt at Olduvai Gorge. This species, one of the earliest members of the genus Homo, has a slightly larger braincase and smaller face and teeth than in Australopithecus or older hominin species. But it still retains some ape-like features, including long arms and a moderately-prognathic face. Because of this  combination of features different from those seen in Australopithecus, Louis Leakey, South African scientist Philip Tobias, and British scientist John Napier  in 1964 declared these fossils a new species and called them Homo habilis.   Such a name, which means ‘handy man’, was given because this species was thought to represent the first maker of stone tools. Currently, the oldest stone tools are dated slightly older than the oldest evidence of the genus Homo. Many scientists think it is an ancestor of later species of Homo, possibly on our own branch of the family tree (Broderick, 2019). 

The most significant fossil discovery of the seventies  was a partial skeleton, discovered in 1974 by anthropologist Professor Donald Johanson and his student Tom Gray in a maze of ravines at Hadar in northern Ethiopia (Gundling, 2010). They eventually unearthed 47 bones of a skeleton - nearly 40% of a hominid, or humanlike creature, that lived around 3.2 million years ago. Based on its small size, and pelvic shape, the discoverers  concluded it was a female and named it 'Lucy'. 

Although Lucy had some features like  a chimpanzee, the structure of her knee and pelvis suggested  that she routinely walked upright on two legs, like us. This form of locomotion, known as 'bipedalism', being  the single most important difference between humans and apes, placed Lucy firmly within the human family (BBC, 2014). 

Subsequently,  her discoverers coined a new species name, Australopithecus afarensis that included not only the Hadar specimens,  but fossils collected by Mary Leakey’s expedition at Laetoli in Tanzania. The latter is renowned for its famous footprint trail preserved in solidified volcanic ash, imparting convincing evidence for bipedalism at 3.6 million years ago. Further investigations showed that more than four million years ago, small upright-walking hominids such as Ardipithecus ramidus and Australopithecus anamensis were living in forest-edge habitats of northeast Africa (Gundling, 2010).  

Darwin’s prophetic prediction  that it was “probable” that Africa was the cradle of humans thus got confirmed.

Development  of Theoretical Understanding  

Events in the decades following the end of World War II   led to a crucial development in theoretical understanding  that transformed human evolutionary studies.  A consensus was reached  that Darwinian natural selection acting on variation arising from random mutation was a sufficient mechanism to explain evolutionary change. 

Focusing on evolution as a process bringing about change in populations over time, rather than merely  paying attention to taxonomy and phylogeny, arguably represents the most significant theoretical shift in thinking about evolution since Darwin. The comparative de-emphasis on iconic types resulted in reduction in hominid names and consequent simplification of hominid family trees. As observed by Gundling (2010), “ … there can be little doubt that the ‘splitting’ taxonomic philosophy of the past where almost every new specimen received a new species or quite frequently a new genus name was in dire need of revision.” 

The de-emphasis of iconic types also modified the concept of evolutionary grades which made clear distinctions between the categories of ape and human. Such a concept  ignored the evolutionary reality that at some point members of the human lineage were very ape-like. This realisation  led to the  acceptance of the South African australopithecines as human ancestors, and the important corollary that bipedalism preceded other distinctive human attributes (Gundling 2010 and references therein). 

New discoveries are not limited to the paleontological record but also include behavioural information. To reconstruct the early hominid behavioural ecology, Sherwood Washburn along with Irven DeVor conducted pioneering  studies of social primates that served as living proxies for modelling (Washburn and DeVore 1961). Washburn reasoned that these ground-living primates were a good model for early human adaptations because they evolved in African savannas alongside ancestral hominins. Leakeys hired scholars to conduct research into the behavior of the great apes as a potential new data source of early hominid behaviour (as quoted in Gundling, 2010). Such studies explicitly addressed questions of evolution of human behaviour. 

Archaeological evidence, which includes any objects that have been made by hominins, played an important part in generating evidence and establishing theories about the behavior of early modern humans. 

As noted by Gundling, (2010), a logical extension of the post-WWII new physical anthropology was concerned with a more holistic picture of our evolutionary past. It was realised that these hominid populations did not exist in a vacuum but were components of complex, evolving ecosystems. Hence, it became necessary to collect more of  contextual data in an effort to reconstruct biological and physical environments in which our ancestors existed and evolved. What early humans ate, how food was acquired and processed, even how it was distributed among members of a social group, became viable questions. 

By the early seventies of the last century some anthropologists challenged the “Man the Hunter” hypothesis  and  an alternative, “Women the Gatherer” that focused on the central role of women in child rearing and gathering of food resources was propounded. Through decades of field research, anthropologists have developed a more flexible  view of human labour. According to this view, women are not bound by biology to gather, nor men to hunt. In fact, by the mid-1980s,  several accounts of women’s hunting in foraging societies had emerged (Venkataraman, 2021). 

Another group of researchers also began to question the big-game hunting scenario.  Archaeologists, geologists, and palaeontologists began working on “site formation processes” to get a better understanding of how assemblages of fragmented animal bones and stone tools came to be commingled. Over the next few decades, often with recourse to modern ecosystems as analogues, one of the main conclusions suggest the potential importance of scavenging (Little, 2020), Man the Scavenger. 

As recognised in the beginning, human evolution studies involve multidisciplinary approach. Two post-WWII developments have revolutionized the empirical base supporting human evolution and immensely improved our understanding of the subject: genetics and dating techniques. 

References 

Balzeau, A., Buck, L.T., Albessard, L., Becam, G., Grimaud-Hervé, D., Todd, C. R. and  Stringer, C.B.,  2017.  The Internal Cranial Anatomy of the Middle Pleistocene Broken Hill 1 Cranium.  PaleoAnthropology, 2017: 107−138.  doi:10.4207/PA.2017.ART107

BBC 2014.  Science & Nature - The evolution of man" . Mother of man - 3.2 million years ago. (http://www.bbc.co.uk/sn/prehistoric_life/human/human_evolution/mother_of_man1.shtml)

Brain, C.K. 2003. Raymond Dart and our African origins,  in  A Century of Nature: Twenty-One Discoveries that Changed Science and the World, edited by Laura Garwin and Tim Lincoln, published by the University of Chicago Press.

Broderick, C.,  2019, The Discovery of “Zinj”, The Leakey Foundation, Guest Post, Today in History, Published on 07/12/2019.

Dart, A.R., 1925, Australopithecus africanus: The Man-Ape of South Africa. NATURE,  No. 2884, Vol. I I5, pp. 195 – 199.

Goodrum, M.R., 2009. The History of human origins research and its place in the history of science: Research problems and historiography. Hist., Sci., xlvii (2009).

Gundling, T., 2010. Human Origins Studies: A Historical Perspective. Evo Edu Outreach (2010) 3:314–321. DOI 10.1007/s12052-010-0248-7

Little B. 2020. Early Humans May Have Scavenged More than They Hunted.  https://www.history.com/news/prehistoric-human-diet-scavengers-vs-hunters. Jan 9, 2020.

Taung Child, 2020. https://humanorigins.si.edu/evidence/human-fossils/fossils/taung-child

Venkataraman, V., 2021. Women were successful big-game hunters, challenging beliefs about ancient gender roles. The Conversation, March 11. 2021.

Washburn SL, DeVore I. The social life of baboons. Sci. Am. June; 1961