The human fossil record: the development of adaptation mechanisms

Humans have developed from different origins, and the process of natural selection and evolution shed more light about how they evolved. In the environment, populations also adapt in different ways depending on the environmental features. While describing the development of human beings and adaptation mechanisms, this fossil record report also covers the methodologies that are crucial for understanding how evolution and cultural change take place over time. 

Natural Selection and Evolution 

Charles Darwin, a significant individual in evolution fundamentals, described evolution by natural selection as a process which allows the preservation of favorable individual differences and variations and destruction of harmful individual variations. Natural selection among humans- where there is the preservation of beneficial characteristics- constitutes positive selection (Beauchamp, 2016). A positive, useful trait is one which increases the chances of survival and reproduction in humans, and one can inherit it for continuity. Documented examples of positive naturally selected attributes among humans include the development of lactose tolerance, malaria resistance, and skin pigmentation. 

Regarding lactose tolerance, a significant percentage of people in Europea persisted in the ability to breakdown lactose while others could not survive at the time where utilization of dairy products was very high. The reason behind this according to research is a mutation in the lactase gene (LCT). Malaria is also another infectious disease driving natural selection in humans; for most affected regions, those with favorable traits make them resistant to malaria and survive. A mutation in the Duffy antigen is the desirable trait giving protection against malaria mostly by Plasmodium vivax. 

Population Adaptation to the Environment 

Physical adaptation of humans to their environment includes cold adaptation, heat, and high altitude adaptation. Regarding cold adaptation, the extremely cold climate is favorable for short people with short arms and legs, and flat faces with pads of fat over the sinuses. Such an adaptation is vital to minimize on loss of heat due to a lower surface area to volume ratio (Daanen & Van, 2016). Moderately cold conditions are favorable for tall individuals with moderate fat and narrow nose also to reduce heat loss. Individuals in hot areas are tall and thin, with wide noses and little fat pad for maximum heat loss due to a created large surface area. They also tend to have dark skins to protect them from the effects of solar radiation. 

For individuals in extremely hot places such as deserts, they are generally thin but not very tall since they also need to minimize the water loss by being in a desert. High altitude areas are favorable for individuals with increased lung tissue to maximize the low oxygen levels and as an adaptation for the low pressure. Cultural adaptations in humans involve the change of behavior to facilitate survival in their natural environment. Individuals in very cold places develop a culture of putting on coats to cover them from the cold. Such people may also install fireplaces within their houses for warmth especially during the night when it is extremely cold. Individuals in very hot places would mostly put on light clothing because of the heat. 

Methodology for Understanding Human Evolution 

Methodology for understanding human evolution and change over time is through various disciplines including anthropology, embryology, and genetics. Through genetics, one can study heredity vital in knowing the lineage of human beings and changing genetic traits over time. Current advancements in technology make it possible to examine genetic traits through molecular methods such as DNA testing by ELISA (Enzyme-Linked Immuno-sorbent Assay) processes. Through ELISA methods, it is possible to know the exact genetic make-up of individuals and even identify possible mutations over time to ensure survival. Mutations such as the ones facilitating lactose tolerance among affected individuals as earlier stated in the introduction become evident through genetic study methods. Through anthropology, one studies the evolution of human behavior and their societies over time. 

A significant branch of anthropology is archaeology where there is of human material remains including artifacts to analyze their past behavior. Embryology involves the study of growth and development of human beings to try and shed light on the past. Through embryology evolution, there is the linking of human development to a common ancestry thus vital in understanding human evolution. One scientist considered to base on embryology to understand evolution actively is Post Darwin Evolution scientist by the name Ernst Haeckel who even tried to compare the growth and development of vertebrate species by using embryology. 

Human Fossil Characteristic Comparisons 

	Homo erectus	Homo heidelbergensis	Australopithecus anamensis	Australopithecus afarensis	Homo rudolfensis
Physical properties
First appearance in fossil record and last appearance in fossil record	Discovery in 1891 but believed to have lived between 1.89 million and 143,000 years ago	Discovery in 1908 but believed to have lived between 700,000 to 200,000 years ago	Discovery in 1995 but believed to have lived between 4.2 to 3.9 million years ago	Discovery in 1974 but believed to have lived between 3.85 to 2.95 million years ago	Discovery in 1986 but believed to have lived between 1.9 to 1.8 million years ago
Place found and geographical distribution	Northern, Eastern and Southern Africa  West Asia (Georgia), East Asia (China and Indonesia)	Europe, China, Eastern and Southern Africa	Eastern Africa (Kenya and Ethiopia)	Eastern Africa (Ethiopia, Kenya and Tanzania)	Eastern Africa (Northern Kenya, northern Tanzania and Malawi)
Specialized skills	Use of shells for tool production and engraving ( Joordens et al., 2018)	Built shelters  Skilled at hunting big game animals	Climbing of trees	Climbing of trees
Anatomical features	Expanded braincase relative to the size of the face	Larger brain case with a flatter face than earlier species	Expanded upper end of tibia bone  Long forearms	Brain size was 1/3 of modern human brain  Long, strong arms with curved fingers	Large braincase size of 775cm 3  Larger molar and premolar teeth
Height	145-185 cm	Males- 175cm  Females- 157cm
Weight	40-68kgs	Males- 62kgs  Females- 51kgs		Males- 151cm  Females- 105cm
Sexual dimorphism		Strong sexual dimorphism with males being heavier and taller than females		Strong sexual dimorphism with body sizes between males and females being different
Cultural characteristics
Use of fire and ability to make fire	Used fire and had the ability to make but the extent of their mastery with fire is unknown	Ability to use and make fire especially due to the fact that they lived in colder climates
Primary tool type and characteristic	Hand axes made using stone tool technology	Used wooden spears used for hunting big game animals			Stone tools for food processing
Art work	Making hand axes with stones	Making wooden spears			Stone tools
Personal items found
Religious symbolism found	Cared for the old and the weak

Most of the information in the above table is from the Smithsonian website for natural history (Smithsonian National Museum of Natural History, 2019). 

Sequence of the above human ancestors from the oldest is: 

Australopithecus anamensis 

Australopithecus afarensis 

Homo rudolfensis 

Homo erectus 

Homo heidelbergensis 

The Human Evolutionary Tree 

Mosaic Revolution 

Mosaic evolution is a concept in human evolution which views changes as taking place in one specific part of the body as other parts remain constant. The mosaic kind of evolution is present in the five human ancestors focused in this paper. There is a continuous change in the size of the brain as evolution takes place with most other parts remaining constant. The brain size continues to increase in size with development towards the present human beings. The older Australopithecus afarensis had a brain size only one-third of the modern brain, but this increases in size with succeeding ancestors such as homo rudolfensis with an increased brain size of 775cm3. 

Life on Earth of Hominin 

Based on the fossil records, it is possible that more than one kind of hominin lived on earth. Using evidence from the Smithsonian’s website for natural history, hominins such as Australopithecus africanus and Paranthropus aethiopicus had a moment in time where they existed together in the face of the earth. We, humans, are currently the only type on the planet earth. In my opinion, it might as well be that we have always been the only type. The reason for this is that despite changing environmental conditions over time, there appear to be significant changes in the physical anatomical forms of human beings thus bringing about many questions on the validity of the human evolution theory. Michael Denton, a biochemist, also questions the Darwinian Theory and if it holds water, the main problem being the lack of transitioning in the development of the fossils and what the theory present is a complete product (Denton, 2016). 

Homo Floresiensis 

Homo floresiensis is one of the recent discoveries of human fossils in the year 2003. It probably lived in Asia about 100,000 to 50,000 years ago. Individuals were 3 feet 6 inches tall with small brains and large teeth. There is a possible relation to the human fossil record based on its anatomical features and behavioral activities of making stone tools and hunting animals just like other human fossils found. They had a small body and small brain probably due to their purposed place of stay in the Islands, and a volcanic eruption could be the possible cause of their extinction. Controversies arose of it not being a genuine species, but research proved of it being a valid taxon and a human species. 

Scientific Evidence for Human Evolution 

Besides human fossils, other scientific evidence for human evolution involves the study of genetics, the study of human behavior through tools, paintings and footprints and dating technology to determine the age of collected fossils. The study of genetics helps in relating humans to other primates thus vital in the study of human evolution. It is essential to have multiple lines of evidence for human evolution for comparisons and the accuracy of information obtained. Having only one independent line of evidence increases the probability of collecting the wrong data and consequently giving out incorrect information. 

Conclusion and Reflections 

Hominins have continued to change over time both in terms of physical and cultural traits. There is a continuous increase in the brain size and development of an upright posture as arms develop from being curved to straight. The cultural characteristics also change over time from hunting for food to agriculture as a way of survival. There is also a continuous improvement in the making of their tools from the use of wood to technological advances today. Phylogenetic trees are vital in the evolutionary changes over time just as this context paper. It shows how humans evolved from Australopithecus anamensis to afarensis and finally to present-day humans. However, it is crucial to know that they are subject to change and may not remain the same especially due to change of evidence over time. If for example there is a discovery of a new species, its inclusion in the phylogenetic tree will change the tree. 

References 

Beauchamp, J. P. (2016). Genetic evidence for natural selection in humans in the contemporary United States. Proceedings of the National Academy of Sciences , 113 (28), 7774-7779. 

Daanen, H. A., & Van Marken Lichtenbelt, W. D. (2016). Human whole body cold adaptation. Temperature , 3 (1), 104-118. 

Denton, M. (2016). Evolution: Still a Theory in Crisis . Discovery Institute Press. 

Joordens, J. C., d’Errico, F., Wesselingh, F. P., Munro, S., De Vos, J., Wallinga, J., ... & Mücher, H. J. (2015). Homo erectus at Trinil on Java used shells for tool production and engraving. Nature , 518 (7538), 228. 

Smithsonian National Museum of Natural History. (2019, February 13). What does it mean to be human? [Video File]. Retrieved from http://humanorigins.si.edu/