IN SEARCH FOR THE MISSING LINK
HISTORICAL ASPECTS OF HUMAN
EVOLUTION STUDIES
Thoughts about how we, the humans, came into being prevailed in the scientific community since long. Even the philosophers in ancient times wondered about the origin of life. In Rig Veda (1500 – 1000 BCE) there is a mention of a Hindu sage and philosopher, Lokya Brihaspati, who opined that consciousness (life) emerged from inanimate objects (Sharma, 2013). Anaximander of Miletus, a Greek philosopher who lived in the 500s BCE speculated that humans must have descended from some other type of creature. In the 18th century Linnaeus and others had classified man as a primate, but without drawing evolutionary conclusions. Creationists’ ideas that life and the universe are creations of God are not included here.
A number of publications were instrumental in shaping early ideas of human evolution. Lamarck was the first to discuss human evolution in his book Philosophie zoologique (1809), albeit without acknowledging common ancestry (Wikipedia). Some among other noteworthy publications are Darwin’s Origin of Species (1859) and Descent of Man (1871), Charles Lyell’s Geological Evidences to the Antiquity of Man (1863), Thomas Henry Huxley’s Evidence as to Man’s Place in Nature (1863), and John Lubbock’s Pre-Historic Times (1865).
In this regard it is important to recognise that many important developments in the natural sciences provided substantial foundation for ideas about human origin. Geologists and palaeontologists while working out the history of earth also began to outline the history of life on earth. They discovered numerous Palaeolithic sites in Britain and France that provided clues as to when humans first appeared and what those original humans were like. Geologists began to search for sites containing human artifacts associated with extinct mammals so as to determine how deep in the geological strata one could find evidence for human presence (Goodrum, 2009).
The second half of the nineteenth century is the pivotal period when the study of human origin was revolutionised. Charles Darwin published his famous book On the Origin of Species (1859), elevating the concepts of evolution of life to the status of a scientific theory. Darwin and a contemporary of his, Alfred Russel Wallace, proposed that evolution occurs because of a phenomenon called natural selection, a critical event in the history of human evolution studies. In simple terms, natural selection is the process through which populations of living organisms adapt to their environment, and change.
Darwin’s theory of evolution by natural selection
(Darwin, 1859) is based on the premise that within a population there is
variation in traits, and every population produces more
progeny than its environment can manage. The consequence of this overproduction
is that those individuals with the best genetic fitness for the environment
will produce offspring that can more successfully compete in that environment. Individuals with traits that allow them to adapt to
their environments will help them survive and have more offspring, which will
inherit those traits. Individuals with less adaptive traits will less frequently
survive to pass them on. English biologist TM Huxley coined
the term Darwinism. The modern evolution theory explains
the diversity of life without recourse to
the doctrine of God or any other divine power.
Darwin is rightfully credited with being the most influential, although by no means the first individual to broach the subject of descent with modification, as he put it (for an overview of pre-evolutionary ideas related to human origins, see the references in Gudling, 2010). In 1871 Darwin addressed the implications of evolution theory for the humans in his publication The Descent of man, wherein he suggested that humans had arisen from an apelike ancestor at a remote period in geological past.
Admitting that the veracity of his proposal would have to withstand paleontological scrutiny, Darwin, however, was initially reticent to discuss human evolution in any detail. But his colleague, Thomas H. Huxley harboured no such reluctance when in 1863 he published Evidence as to Man’s Place in Nature: Essays. Huxley’s advantage was that he actually had a fossil human to describe. The first Neandertal fossil recognized by science was discovered in 1856 and he provided a detailed description of the eponymous cranium coupled with carefully composed line drawings (Huxley, 1863).
The Missing Link
The human palaeontology assumed a new importance after Darwin. His idea of common ancestor and the role of fossils in providing evidence of evolution led to the thinking that information about the ancestors to modern humans, the so-called missing link, can be found in fossil records. Perhaps, the most significant impact of Darwin’s evolutionary theory, especially following on the heels of geological antiquity of mankind, was the impetus it created for the search of fossil evidence so as to prove that humans had indeed evolved (Goodrum, 2009).
The discovery of archaeological artifacts along with extinct animals led some people to seek for remains of men who made them. In fact, the search for fossil remains of prehistoric humans had started even before the publication of The Origin of species. The discovery of the first Neanderthal specimen in 1856 in the Neander valley in Germany sparked debates in Germany and elsewhere in Europe, creating an impact on the science of human palaeontology and human evolution.
The study of human evolution through the fossil and archaeological records constitutes a branch of palaeontology and anthropology - Palaeoanthropology. It is an interdisciplinary field wherein evidences from a number of different disciplines and bodies of knowledge converge. For the general theory of evolution, these originally included geology, palaeontology, zoology, botany, physiology, anatomy, and selective breeding.
Here, it is prudent to share the views of Smith and wood (2017) on human evolution. They observe that “given the limitations of the data available to human evolution researchers, Paleoanthropologists are not alone in dealing with contingent, complex, and unique historical events. Among others, cosmologists, astrophysicists, geologists, archaeologists, epidemiologists, and historians share some of our methodological complexities and limitations, and there is much to learn from their insights.…”
Many historians of palaeoanthropology consider that scientific study of human origins began in the nineteenth century at the earliest. Gundling (2010) divides the human origins studies into two very broad periods – one roughly the century between 1850 and 1950, and the other from 1950 onwards. In the former period, theories of human evolution were largely driven by discoveries. Fossil evidence was generally seen as a matter of prime interest to prove evolutionary theory right, leading to a race to find the “missing link” connecting humans and apes. The scientists, being focused on taxonomy and phylogeny, were mainly interested in collecting “missing links,” naming them, and creating family trees. The second period is characterized by the emphasis on the hominids themselves as well as on the ecological context, both being of equal importance.
Gundling (2010) underlines two important developments in the human origin studies during the mid-nineteenth century. The first is the acceptance of a temporal association of human material culture (stone tools) with extinct Ice Age mammals. This was significant in that it opened up a considerable prehistory for the human species. The second is the publication of a number of scientific papers and reports on the subject immediately after 1850. Most scientists accepted the overwhelming morphological and embryological evidence in support of the close evolutionary relationship among humans and the “man-like” apes, and consequently an ape phase of human ancestry. This acceptance was in no small part due to Huxley’s meticulous comparison of gorilla and human anatomy (Huxley, 1863) in which he concluded that the gorilla and its close relation, the chimpanzee, represented the nearest approach to humanity in nature.
The discovery of Neanderthals galvanised the search for more ancient, primitive “missing links”. The search got further boost in 1890s by the discovery of a skull and a femur in a geological deposit containing Pleistocene mammals at Trinil on the island of Java by a Dutch physician, Eugene Dubois. The fossils (estimated to be between 700,000 and 1,000,000 years old) appeared to be that of an early human (Java Man) with a much smaller cranial capacity relative to Neanderthals or Homo sapiens. The apelike morphology of the skull and humanlike femur led Dubois to announce that the find is the evolutionary link between apes and humans and the species was named by him Pithecanthropus erectus (Ciochon and Huffman, 2018). Today, more than 100 skeletal specimens have been attributed to this species from localities in Central and East Java. This find bolstered the conventional wisdom at the time that humans first evolved somewhere in Asia. Though Darwin had tentatively suggested Africa, for some time Asia came to be regarded as the most likely place for the cradle of mankind.
Then in 1907 quarry workers in Germany found a fossil human jaw, which the German palaeontologist Otto Schoetensack called Homo heidelbergensis. In the following year a Neanderthal skeleton was discovered in France. With a number of fossils being discovered in Germany, France, Belgium, and Britain, Europe also entered the race to find the first human. The recovery of additional Neanderthal remains in Europe reinforced the interpretation that the latter was representative of a population of archaic humans occupying Ice Age Europe (Veldhuis et al., 2014).
During the early
twentieth century, the significant early hominid fossil discovery brought about
wide acceptance of evolution of humans in scientific circles, even though large
segments of the lay public remained skeptical. In any case, though the "missing link" remained elusive, the basic premise
of biological change through time was affirmed (Gundling, 2010).
References
Ciochon, R.L. and Huffman, O.F. 2018. Java Man, Encyclopedia of Global Archaeology, July 2018. https://www.researchgate.net/publication/326681417.
Darwin, C. R., 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray; 1859.
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).
Sharma, S. K. 2013. Charvak Darshan (Dharm ke dhande ki pol ka darshan) (in Hindi) pp 628. 2013, Vishv Books Private limited. India. ASIN B0764DYPTJ. ISBN 9350652331,
Smith, R. J. and Bernard, W., 2017. The principles and practice of human evolution research: Are we asking questions that can be answered? C. R. Palevol 16 (2017) 670–679. http://dx.doi.org/10.1016/j.crpv.2016.11.005
Veldhuis, D, Kjærgaard, P.C. and Maslin, M., 2014. Human Evolution: Theory and progress. https://www.researchgate.net/publication/27088054 DOI: 10.1007/978-1-4419-0465-2_642
To follow next - Africa, the cradle of mankind.
Very interesting observation and a good summing up of the references on 'missing link'. The same story/puzzle, I believe, also applies to the lower animals in the geological past between reptiles and birds.
ReplyDeleteEvolution, though is un-denying, the natural selection appears to be a more governing factor in appearances of different species. Although not an expert on the subject, sometimes I tend to infer that the present day Dragons are the modified forms of dynasaurs.
Thanks for your comments. I agree with you that the same principle applies to the lower animals in the geological past, governed by the natural selection.
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