Conclusion

Homo sapiens sapiens came to be because of evolutionary patterns that have occurred throughout earth’s lifespan. It began with a split between monkeys and great apes, and great apes into habitual bipedal primates, such as the Australopiths and the species below that share that same taxonomic classification. After the Australopiths came the genus Homo. It began with Homo habilis, with Homo erectus coming shortly thereafter. Homo habilis was the first subspecies in the family Homininae to leave Africa. Following this, the genus Homo spread its population all over the eastern hemisphere. Neandertals came to be following the evolution of Homo erectus (supposedly). Neandertals remained in locations other than Africa. It was finally after the evolution of the Neandertal that H. sapiens sapiens came to exist. Neandertal genes still exist in populations outside of Africa, suggesting that there was limited interbreeding between Neandertals and primitive Homo sapiens sapiens. Because humans came to be so long ago, there is a question surrounding the evolution of H. Sapiens’ behavior. It is suggested that life spans increased as time advanced and behavioral evolution followed. This is how the modern H. Sapiens sapiens (as we know ourselves) came to exist today.

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.

Survival and Success of Bipedal Primates

Survival Issues:

• the need to find new food and water sources after the thinning of the forests took place 
• the threat of very large, roaming predators 
• increased exposure to the sun 
• increased difficulty in birth and raising of young due to longer maturation periods

Physical Characteristics that helped/hurt bipedal primates facing these issues:

Helpful Traits:

Bipedalism

The most important factor in the switch to bipedalism is the freeing up of the hands. A change in locomotion and how this species got around also made them more stable walkers and even developed into the ability to run. Bipedality was helpful in finding food because it allowed primates to see over longer distances on the savanna and the bipedal stride helped them expend less energy when walking long distances foraging for food and water. Becoming migratory could have been new to these bipeds, and introduced them to the potentiality of traveling around and surveying new landscapes with better food sources. Traveling longer distances could have helped these species avoid predators, as their bipedality made them less effective at escaping danger. Standing upright also made it easier to get food from low hanging tree branches. A standing posture made them appear bigger and more threatening as well.

Bipedalism also reduced the amount of sun exposure these primates were experiencing since they no longer had their backs toward the sun. As the the forests began thinning during this time, the intensity of the sun could have become much greater. The need to be able to release body heat is common in every animal, and is typically done through panting. As humans, we do not pant. We release body heat through sweat glands located under the surface of our skin. It is possible that the development of these sweat glands is what allowed for the loss of hair that we begin to see in these species.


A Precision Grip

It is thought that Homo habilis was the first of the bipedal primates to begin perfecting the use of tools. It is obvious that this is not a characteristic that developed overnight, but one that took time and patience. As the bipedal primates began to use tools, their hands began to change. They developed longer and stronger thumbs due to the pressure applied to it while using tools. Also, their fingers became more flexible and dexterous. These better grasping and manipulating hands allowed them to use tools to fight predators (like throwing stones) and meant they were better at handling those tools to protect themselves. The beginning of tool use possibly led them to begin cooking their food, though we are not sure when this took place. Cooking was very important to the success of these species, as it allowed for a much higher caloric intake without a high energy expense.


Omnivorous Diet

The ability to process different types of food effectively was probably one of the most important evolutionary adaptations that took place in bipedal primates. When their diet began to include more meat, it led to the evolution of smaller, sharper teeth and a more slender jaw, better for processing this wider range of foods. Those with flatter teeth were better suited to process plant foods. As they began to eat meat and other sources of protein, whether it be from scavenging or hunting, it paved the way for encephalization. It is thought that due to the change in diet, the temporal lobes and the prefrontal cortex of these primates began to grow disproportionate to the rest of their brains. This is important because the temporal lobe controls communication skills, while the prefrontal cortex is responsible for complex decision-making and social behavior. Another important change in the bipedal primates diet was the addition of starch. Studies on the saliva of humans versus the saliva of chimpanzees show that humans produce an enzyme called amylase, which breaks down starch into sugar, while chimpanzees and other animals do not posses this quality.

Impeding Traits:

Bipedalism

A possible disadvantage to bipedalism is the loss of the ability to climb. The development of bipedality meant primates developed stronger legs and weaker arms which made it increasingly harder to live in trees. The changes in foot structure made it difficult to grasp, causing more problems surviving or finding shelter in an arboreal environment. This put them in more danger because bipedal primates were slower at running from quadrupedal predators and could no longer use the trees to escape.

Encephalization

The growth of large brains could have been an impeding quality in that birth became much more difficult and dangerous. It also made the raising of offspring a slow and difficult process due to the long maturation period required to finish the development of the brain.

How Does the Theory of Evolution Apply to Bipedal Primates?

We are using the theory of evolution as a statistical concept to measure changes in the gene pool of bipedal primates. Homo sapiens (modern day humans) share a common ancestor with chimpanzees and bonobos. This ancestor existed 6 million years ago. It was ape-sized in body and brain. It had long arms and a grasping foot to dwell in trees. Sexual dimorphism occurred in this species. They were quadrupedal and had a diet consisting of fruit and leaves. Over the last 6 million years, bipedal primates have adapted to their changing environment and created the taxonomic subfamily of Homininae. Several Hominin species have existed over this time but humans are the only remaining hominins today.

There are two main categories of Hominins:

-Australopithecus genus
-Homo genus

Australopithecus

The Australopithecus were first discovered to have existed around 4 million years ago in Kenya. They were a highly successful genus and persisted for about 3 million years. Over time they migrated to South Africa.

A few traits define this genus:

-brain size: 390-515cc

-shorter, more bowl-shaped pelvis

-bipedalism, but some arboreal living

-big toe curved to grasp branches

-square ankle joints, useful for climbing trees

-inhabited woodlands

-small canines, but larger, more flat molars

Homo Genus
The Homo genus began to appear around 2.4 million years ago in Tanzania, Indonesia, and Europe. (not all at the same time) They retained many of the same traits as the Australopithecus except for a few changes.

These are those changes:

-brain size increased to 1,250cc

-development of large knees, and hips

-stabilization of the trunk with thicker lumbar vertebrae

-loss of hair

-inhabited savannas

-lacked forelimb adaptation for climbing

-tool use, and forging of weapons to hunt

-smaller molars due to the richer, more diverse diet

The differences in the anatomical structure between these two genus', and the locations of the discoveries of their remains suggest that gene flow, as well as genetic drift, impacted the genetic mutations that began to manifest in these life forms. Having to learn to adapt in a new, more arid environment, natural selection pushed for the recurrence of three major traits to create the Hominin species.

These traits define the Hominin species:

-habitual bipedality

-reduced canine size

-increased brain size


Bipedalism
The biggest change in the development of early primates was the switch to bipedalism, or walking upright. It is unclear why early humans adapted to bipedality, but it is thought that the climate changed, causing trees to recede and develop into a savanna. Bipedality is beneficial in both terrestrial and arboreal environments, but standing upright on a savanna makes it easier to spot predators over the tall grass. Habitual bipedalism honed this species' body to be able to run, which is probably how they hunted for food. Being able to run and carry tools could have made them more formidable to smaller prey.

With the switch to bipedality came a lot of physical changes.

These include:

-A change in the center of gravity, moving from the center of the torso in quadrupeds to the pelvis in modern humans. When walking, the center of gravity shifts from one side of the pelvis to the other. The pelvis shape became shorter and more bowl shaped. The narrowing of the pelvis along with the increased brain size made birth difficult, which could be the reason why they developed the need for longer postnatal nurturing periods.

-A change in foot structure: bipedal primates have lengthened feet with arches to support standing. Though this helps with standing upright, it means that our feet can no longer grasp well.

-Weaker and shorter arms began to develop in bipedal primates since so much pressure was put on the use of legs. They also developed stronger, more dextrous hands with opposable thumbs. This allowed for better tool use and an increased ability to carry and tend to babies.

Reduced Canine Size
Throughout the development of these early Hominin species there were constant geographical changes taking place. Continental drift impacted the environments of these species and in turn affected their food sources, possibly causing the leafy vegetation and fruit sources to be unavailable. With this change in diet came the reduction in canine size and the thickening of the enamel of the teeth, especially in the molars. This thickening of the enamel was present in the Australopithecines, but eventually faded out in the Homo genus due to the much more varied diet.


Increased Brain Size
It is possible that varying terrain scenarios, as well as changing climates, pushed these species to find new ways to survive. The crucial change in environment occurred with the switch from a woodland surrounding to an arid savanna. The change in our setting caused our every day lives to become different, and in reaction to these stimuli our brain began to develop and grow. The change in brain size that occurred in the Hominin species suggests that these primates had the cognitive capacity to adapt and thrive in different environments, thus leading to their expansion.

Behavioral Changes

As we moved out onto the savanna we left behind our old way of foraging in the trees and using them for shelter. On this new terrain we developed and honed many skills that would lead us to eventually inhabit the globe. A few of these early behavioral changes were critical to our survival.

Becoming nomadic
The ability to run long distances and travel to new places in search of food was vital to the survival of early bipeds. We became nomadic in order to scavenge game killed by carnivorous predators and migrate to new vegetation supplies. By nomadic we mean that these species followed food sources, which could have been the driving force for them to leave Africa. The term should not be confused with the more modern definition of nomad, which is a person who herds livestock to different regions to graze dependent upon the seasons.

Tool use
The beginning of tool use and the transition from the Old World Olduwan tool set to the new, more versatile Achuelian set was an important behavioral change as well. With this new "Swiss army knife" of stone tools, early bipeds began to transport their tools with them to use in new environments. This foresight is something that had not be considered before.

Development of social groups
The final, most prominent behavioral change is the development of social groups. It proved advantageous to early bipedal primates to create social groups most importantly to insure the success of offspring. With the increase in brain size, and the narrowing of the pelvis, birth was no longer something that could be done alone. Also, maturation of offspring was a slow and intensive process since the brain was not able to fully develop in utero.

These behaviors developed at different times and places as a response to external and internal stimuli- as evolutionary answers to what life threw at them. Changes in this species' gene pool and repetitive selection to create a phenotype capable of coping with varying terrain and climate, created a more cognitive brain that gave bipeds the ability to change their behavior and learn from their parents.

Wild or Domesticated?

What is the difference?  

Domestication is the process by which species are genetically modified over time through their interaction with people.  Animals that coexist with humans are bred for traits that are most desirable or useful to those humans. When certain traits are selected for and manipulated by people, over time the genetic makeup of the species evolves into something different from its wild ancestors. These new genetics often leave the animals unfit for their natural environment because traits favored by people are not the same as those favored by nature. This creates a dependence on humans for survival.  This is different from tamed animals because taming does not change a species’ genetic structure, it only trains specific animals to adapt to human control. 

Wild animals are  those living in their natural state, uninfluenced by human control.

Here are some examples:

Dogs and Wolves:

• Dogs go into heat twice a year, while wolves only go into heat once a year.
• Wolves have the ability to bite into bone very quickly, whereas a dog has lost this ability.
• Wolves are carnivores and could not survive on dog food.
• Wolves live in packs and cannot live alone, like some dogs do.
• Wolf cubs are born black no matter what color they will end up as an adult.
• Unlike dogs, wolves rarely bark.
• Wolves hide from danger, while a dog's instinct is to protect.
• Usually, dogs mark their territory in one spot while wolves tend to mark anywhere.  They sometimes mark on females and sometimes with feces.
• Anybody can own a dog but in some states it is illegal to own a wolf.  Where it is legal, one must construct a special fence to obtain the necessary permit.

 

Wild and Domesticated Turkeys:

• Since they are bred to grow quickly and look pretty, domestic turkey strains no longer have the survival skills to make it in the wild.
• There is selective pressure on genes related to growth and coat color in domesticated turkeys, resulting in their inability to fly (larger bodies) and run fast (shorter legs).
• Domesticated turkeys are almost twice the size of wild turkeys.
• Wild turkeys display more heterozygosity than commercial turkeys, meaning they have greater genetic variation.
• Wild turkeys have traits that help them survive in the wild like sleek, tall bodies, long legs and great eyesight.
• Wild turkeys make less noise than Domesticated turkeys, most likely because noise attracts predators in the wild. 

Through thousands of years of human manipulation, commercial turkeys have become very different from their wild counterparts and ancestors, the Mexican Wild Turkey. Since turkeys are bred for food, humans have selected for traits like large body size-generation after generation. Though good for food, this trait leaves the new, significantly larger-bodied turkey population unable to survive in the wild and completely dependent on humans. Wild turkeys, on the other hand, have traits selected for their survival by nature. These genetic changes are an example of evolution because over time, domesticated and wild turkeys have had different parties selecting for their traits. Domesticated turkeys and wild turkeys have significantly different genetic makeups because they require different traits to survive and reproduce in their respective environments.

The Eight Mechanisms of Natural Selection

Natural selection is the driving force of evolution. For any adaptations or evolution to occur, the population’s genes need to go in a certain direction. The processes listed in our introduction to evolution do not change the overall makeup of a population or move it in any one direction, that is natural selection’s role. This means that some alleles must become more common and others must become less common. Natural selection occurs when the environment favors one trait over another and causes traits to increase or decrease in a population. A trait is selected for when individuals with it are better suited to survive past reproductive age and produce offspring with that trait. Since those with the favored trait are reproducing, that favored trait becomes more common in a population.


The eight mechanisms of natural selection are:

1. All species are capable of producing offspring at a faster rate than food supplies increase.
2. There is a biological variation within all species.
3. In each generation more offspring are produced than survive, and because of limited resources, there is competition among individuals.
4. Individuals who possess favorable variations or traits have an advantage over those who don't have them.
5. The environment context determines whether or not a trait is beneficial. What is favorable in one setting may be a liability in another.
6. Traits are inherited and passed on to the next generation because individuals who possess favorable traits contribute more offspring to the next generation than others do. Over time those favorable traits become more common in the population while less favorable characteristics are less common and become weeded out.
7. Over long periods of time, successful variations accumulate in a population, so that later generations may be distinct from ancestral ones. Thus, in time, a new species may appear.
8. Geographical isolation also contributes to the formation of new species. As populations of a species become geographically isolated from one another, they begin to adapt to different environments. Over time, as populations continue to respond to different selective pressures, they may become distinct species.

Introduction to Evolution

Definition: The theory of evolution, as described by Dr. Chipley, is a statisical concept; a change in traits and characteristics from one generation to the next. Evolution explains how variation occurs.


Evolution is separated into microevolution and macroevolution. Microevolution is the smaller changes in a species, like changes in allele frequency. Macroevolution describes changes that occur over a long period of time, like the evolution of a new species.


Evolution is a two step process:

-The production and redistribution of variation

-Natural selection acting on that variation.


The processes of evolution that produce and redistribute variation are :

1. Mutation- When one allele changes to another and the gene itself is altered. This contributes to variation because that genetic change is passed on and spread to the next generation, where it changes the genetic makeup of the population over time. Mutation is the only way to produce new genes.

2. Gene Flow- Gene flow is the exchange of genes between populations. So when individuals of one population mate with those of another, their genes are mixed and offspring will have genes from both populations(meaning possible new traits to be passed down).

3. Genetic Drift- Evolutionary changes in allele frequencies that are produced by random factors in small populations. In a small population, if an allele is rare it may completely disappear if not passed down. Also, a rare allele could become more and more common as shown by the Founder Effect. This occurs when a small group forms a colony and mates within itself. The genes passed down are those of that small group of founders and something rare in the parent group may become common in the small new group.

4. Recombination-When members of chromosome pairs exchange DNA segments during meiosis. Genes sometimes are brought to new genetic environments and can be influenced by the alleles they are close to. This change in environment can change the way a gene acts and changes of gene function can be acted on by natural selection.