The belief that humans originated in Africa is widespread. However, it is not widely understood how the specific ecological characteristics of Africa were responsible for the critical evolutionary transitions from forest-dwelling fruit eaters to savanna-dwelling hunters. These were predicated on earth movements and physically aided by Africa’s seasonal aridity, soils originating from bedrock, and lack of barriers between the north and south.
These characteristics fostered vast savanna grasslands characterized by unpredictable rainfall, frequent fires, and an abundance of different grazing and browsing animals.
My life’s work has centered on the ecology of Africa’s huge herbivores and their impact on savanna vegetation. In my most recent work, I explain how unique ecological characteristics of these creatures, based on Africa’s physical topography, enabled the adaptive modifications that ultimately led to the evolution of modern humans.
The realization that this remarkable evolutionary shift could only have occurred in Africa emerges. This designation highlights the profound cultural legacy created by Africa’s large mammal heritage for the whole human race.
In the late Miocene, approximately 10 million years ago, a plume of molten magma, a hot, liquid substance from deep under the Earth, drove the eastern portion of Africa upward. This resulted in rifting of the Earth’s crust, volcanic eruptions, and mineral-rich soils from lava and ash. Grassy savannas expanded, and animals were increasingly adapted to graze this plant component. During this period, apes were compelled to spend less time in the trees and more time on two legs.
Early ape-men (Australopithecines) were compelled to alter their diet as a result of a decline in precipitation that limited plant growth and exacerbated dry season aridity. They shifted from ingesting primarily fruits from forest trees to underground bulbs and tubers found between the branches. This was difficult to extract and chew.
This resulted in the evolution of the genus Paranthropus, also known as “nutcracker man” due to its enormous jaws and teeth. Approximately one million years ago, they disappeared. Evidently, the extraction and processing of these well-protected plant sections proved too difficult.
HOMO HABILIS
Another lineage diverged from the australopithecines some 2.8 million years ago, reversing the trend toward strong teeth. This lineage chipped stones to use as tools. These were used to scrape flesh from carnivore-killed animal carcasses and shatter open lengthy bones for their marrow. This ecological change was so significant that it required a new genus name: Homo, especially habilis (“handyman”).
Thus, the earliest humans were scavengers of animal remains. They likely took advantage of a noon window when the murderers, primarily sabre-tooth cats, were sleeping, before hyenas arrived at night to consume the leftovers. Walking upright allowed their arms to transport bones to safe processing areas to supplement their plant-based diet.
Homo habilis dropped their body hair to enable midday movement; this allowed them to be active in settings where animals with fur would quickly overheat.
HOMO ERECTUS
Several hundred thousand years of incremental gains in upright walking and brain capacity led to the next major adaptive shift, which was typified by the development of stone tools. Stone cores were fashioned on both sides in order to facilitate the processing of animal carcasses.
This resulted in the appearance of Homo erectus approximately 1.8 million years ago. These primitive humans had evolved into proficient hunters. Thus, meat and bones became viable year-round food supplies.
A division of labor occurred. Men hunted, and women collected plant parts. This necessitated a home base and more complex modes of communication regarding planned expeditions, providing the groundwork for language.
HOMO SAPIENS
After 800,000 years ago, heat and aridity swings in Africa became more intense. Around 300 thousand years ago, the transition into the Middle Stone Age was marked by the appearance of modern Homo sapiens in Africa and the use of finely manufactured stone tools.
In spite of their hunting prowess, the population of Homo sapiens in Africa had dwindled to a dangerous level by 130,000 years ago, following a particularly brutal ice period. Genetic evidence indicates that the continent’s whole human population decreased to fewer than 40,000 people, who were dispersed thinly from Morocco in the north to the Cape in the south.
One remnant survived by using marine resources while inhabiting caves near the southern Cape coast. This steady food source encouraged the development of tools and even the earliest forms of art.
Approximately 60,000 years ago, the adoption of bows and arrows as weapons, along with spears, likely played a major role in the migration of humans beyond Africa. They spread throughout Asia and Europe, eventually displacing the Neanderthals.
Additionally, hundreds protest the energy crisis in South Africa.
ONLY IN AFRICA: MAMMALS
As described in my book, it was the quantity of medium and large grazers in fertile savannas, concentrated near water during the dry season, that permitted the evolution of a relatively weak ape in Africa to evolve into a feared hunter.
The seasonal dryness that inhibited plant growth in Africa’s eastern and southern areas was caused by the continent’s high interior plateau. Widespread soils resulting by volcanism were sufficiently rich to enable the expansion of medium-to-large grazers equipped to efficiently digest dry grass.
These very numerous herbivores congregated around the surviving waterholes, leaving behind sufficient leftovers of flesh and marrow to make scavenging a reliable method for overcoming shortages of edible plant parts throughout the dry season. The growing reliance on meat to supplement a plant-based diet led to social coordination between male hunters and female gatherers, which drove advancements in communication and tool technology backed by cranial capacity expansion.
MAMMALS AND EVOLUTION
This would not have been conceivable if Africa had remained mostly low-lying and nutrient-depleted like most of South America and Australia.
Expanding human settlements are currently displacing Africa’s nomadic grazers, such as the wildebeest, from their protected areas. As crucial contributors to our evolutionary origins, these creatures represent a global cultural legacy. We must ensure that enough space exists in Africa for these species to survive, despite the rising human population.
»Africa: Large beasts affected human evolution«