How Can We Explain Modern Humans?

Almost 1.8 millions years ago, modern humans began leaving Africa. A migration swept out into Asia and another went North into Europe. It is thought that the migration into Asia honed Homo sapiens into the world-dominating species we are today, and that the European migration eventually just faded out. Why did the Asian group go on to succeed, and not the European group? Anthropologists have yet to land on a decisive conclusion to this question.

Fossil evidence all across Europe has pointed to a few characteristics of the modern European humans, also known as the Neandertals, that could explain the reason for their extinction. First, let's look at a little bit of their history.

In Alta Puerca, Spain there is an archaeological site called the "Pit of Bones". This site is believed to be a mass grave, and contains some of the oldest remains in Europe dating back to 500,000ya. The variation in skeletal structure from the remains found at this site has led scientists to believe that the humans who were buried here were a subspecies of the genus Homo known as H. Heidelbergensis. It is thought, based on fossil evidence, that these were the first of the Homo genus to occupy Europe, and that they would later evolve into H. Neanderthalensis.

The first Neandertal fossil was found in a cave in the Murs Valley, Belgium. These fossils showed beings with very large heads, thick brow structures, and heavy set bodies. It would have suited these individuals well to be so large, as they would have endured repeated glaciation periods. By comparison, Neandertals had larger, differently shaped brains than Homo sapiens. While the frontal lobe was of the same proportion seen in Homo sapiens, the rest of the brain was fairly elongated. An elongated brain would result in smaller parietal and temporal lobes. These lobes are important to memory, cognition, and spacial location. The reduction in size of these parts of the brain is one reason why it is believed that this species went extinct. A second reason is the dietary pattern of Neandertals. They were mostly carnivorous. Based on artifact finds in correlation with fossil remains of Neandertals, it has been deduced that they were superb hunters and mostly hunted large herbivores such as Mammoths. In looking at the Neandertal toolkit, researchers have found that their weapons for hunting required them to get close to their prey in order to kill it. This resulted in various injuries, which could have been fatal in such climates. Wounds have been found on fossil remains and the oldest Neandertal specimen, in regards to age at death, is 30 years old. These individuals lived rugged and taxing lives, and because of an inferior tool kit, may not have been able to stand up against the prevailing technology of H. sapiens.

About 60,000 ya, a devastating drought in Africa resulted in a massive population crash about 200,000 ya. This drought led Homo sapiens to disperse across Asia, where they took some very specialized tools with them. Because of the decimating drought in Africa a lot populations of H. sapiens were pushed to live on the coastline and there it is thought that they began to eat shellfish. A different tool kit that used bone and newly created projectile weapons could have allowed these individuals to flourish in other regions as the climate began to improve. H. Sapien's movement throughout Asia and into Europe can be tracked by the extinction of large mammals such as mammoths and cave lions. The slender, agile bodies of the H. sapiens required less energy consumption than that of Neandertals, and gave them yet another huge advantage.

It is important to address the dispersal of modern humans and our resulting success when attempting to explain modern humans. Over time, through the archaic era and into the modern era, culture and biology have created a sort of flow for our evolution, and the selection of certain traits. This is known as biocultural evolution, and can be defined as a pattern of human evolution in which the effects of natural selection are altered by cultural inventions. Thus, culture can alter the direction of evolution by creating non-biological adaptations to environmental stresses.


Examples:

-Wearing insulated clothing on a cold day reduces the need to adapt biologically in order to cope with harsh weather conditions. This cultural innovation has allowed humans to remain essentially tropical animals, but still be able to live in colder regions.

-The use of fire was probably one of the most important cultural inventions in the evolution of modern humans. The ability to create fires is culturally transmitted, meaning we have no innate ability or sense to create fires.  Since we learned that it aids us in many ways, we pass on that ability to future generations. With the evolution of cooking food, our teeth and stomachs got smaller, and the length of our intestines was altered. Cooking food is also thought to have aided in the growth of human brain size, because it allowed humans to digest food more easily, and therefore gain more nutrients more quickly.


Biocultural Evolution

Culture is defined as the behavioral aspects of human adaptation, a set of learned behaviors passed from one generation to the next by nonbiological means. Humans form cultural traditions and constructs that support the survival of the species. Biology refers to the adaptation and transmission of genetic information from generation to generation. Though culture and biology refer to different forms of adaptation, they have a great influence on each other. Biocultural evolution explains this interaction between culture and biology in influencing human evolution. It states that biology makes culture possible and culture influences the direction of human evolution.

Culture Is a fundamental part of biology. Neuroscience studies have shown that people of different cultures' brains show up differently on MRI scans and they often have different brain structure and hormonal makeups.

Situations that exemplify biocultural evolution:

New information (watch The Science of Sex Appeal) on mate selection in modern humans suggests that women prefer different characteristics in men during different phases of the menstruation cycle. There are two phases to the cycle:

· Follicular phase or ovulation period

· Luteal phase or menstruation period

It has been shown that women tend to choose more dominant qualities such as a deeper voice and the exuding of confidence during their follicular phase. During the luteal phase, women are more disposed to feminine qualities such as a smaller build or caregiving. These natural processes help us to choose a mate that is suitable for us.

But what happens when a woman is on birth control?

A study conducted at Paris-Lodron-University showed that changes in the grey matter of the brain occur during the follicular and luteal phases in women who are not on contraceptives. Women who are on contraceptives, however, show little to no changes in the quantity of grey matter in their brains during these phases. These changes in the brain affect mate selection, and are hypothesized to be a contributing, but minimal, factor in recently increasing divorce rates.

Final example:

FOXP2 is the first gene found that is relevant to the human ability to develop language. According to a study done at the Max Planck Institute for Evolutionary Anthropology, sequencing of the FOXP2 gene in other primates revealed that two evolutionary changes occurred in the protein coding part of the gene after the split in human lineage from chimpanzees, but before the splitting of Neandertals from modern humans. This dating makes it doubtful that the FOXP2 gene prompted the arrival of language, but rather that language was already present and having an impact on the biology of our vocal organs. The selection of a more modern FOXP2 gene would give an individual more refined control of their language, resulting in a more successful organism. On the back side of this observation is that the mutation of the FOXP2 gene, which is responsible for the severe language disorder known as autism, could have allowed for the eruption of creativity marking the advent of behaviorally modern humans.