What Makes Us Humans?

What Makes Us Humans?

Sebastián Escobar & Melisa Sánchez

Getting A Grip On Things

Traveling On Two Legs

Getting A Grip On Things

Traveling On Two Legs

• Our muscles compared to other primates are larger, and we even have more than them to add control and force in the movements.
• The flexor pollicis longus muscle is the most helpful and powerful muscle we have, and which is absent in chimpanzees.

• An advantage of bipedalism is the search and transportation of food, bipedal organisms can use their free limbs to transport food, not like the quadruped organisms, they can´t use their forelimbs to transport something while using them to move.
• One of the most important advantages are the free forelimbs, while just using two rear limbs to transport they can use the free limbs for protection, like the bears, for using tools properly, like humans, or even to fly, like the birds.

• The picture below shows the evolution of the hand; from the hand of a baboon to our hand. You may see the hand of the baboon is smaller, short fingers, including the thumb which is relatively small, then the hand evolved and adapted to a better design and structure for swinging from trees to trees (orangutan hand), the hands became bigger, larger fingers, short thumb and bigger palm. From the orangutan the chimpanzee hand was even bigger, wider and basically more fat, and the last difference different from the mentioned is the thumb grew, still it was smaller to the proportions of the hand. Our hand evolved from the chimpanzee and it is proportional the thumb is larger and the fingers shorter and wider than the rest.

• Humans are the only animal on Earth to have a FULLY opposable thumb.
• Opposable refers to place itself opposite to another object.
• Most primates can oppose their thumbs, but just to their index finger while humans can oppose their thumb to all the fingers.
• Fingers do not have muscles to control them, hand muscles control them.
• Human thumb can move in 6 different ways.

• The spine is curved.
• "S" shape.
• Lateral: Curved shape.
• Frontal: Straight.
• It works as a support structure of the body.
• The spine supports about half of our weight.
• It protects the spinal cord and its nerves.
• It allows us stand upright.

• There are two types of grips: precision and power grip.
• The thumb helps to make opposite pressure to the rest of the finger while grasping and object.
• Thumbs are essential for both of these grips.
• Precision grip: is implemented when precision is required in the movement
• Throwing grip.
• Power grip: is implemented when force, strength is required in the movement.
• Clubbing grip.

• Primate hands are characterized for having one small and short thumb, mixed with long, curved fingers. The human hand is much larger, mobile and muscular, plus they have a fully opposable thumb and short, straight fingers.
• Phalanges have gained larger tufts which have a broader support, the fat “pads” distribute the pressure while we are holding an object, and due to fiber they can accommodate to uneven surfaces to have a better grip.
• Enlargements of the base and in thickness (robustness) contribute to the ability we have with our hands.

• Bipedalism refers to locomotion (ex. walking, jogging, running, etc.) on two legs.
• Bipedalism is the ability to use two feet for movement. Bipedal organisms like humans or kangaroos use their two back limbs to move.
• We are clumsy, slow and susceptible to injuries.
• Multiple theories on why we developed bipedalism.
• There are two types of bipedalism: facultative bipedalism and habitual bipedalism.
• Facultative bipedalism: bipedalism assumed on a temporary basis.
• Habitual bipedalism: regular bipedalism.

Precision Grip.

Power Grip.

Traveling On Two Legs

All Brains On Board

Traveling On Two Legs

All Brains On Board

• Walking upright has benefits and costs. The benefits include reaching easier fruits and other food from trees and higher objects, freeing the hands for carrying tools, babies, food, objects in general, somehow giving them defense because they looked bigger and more intimidating to predators, generally speaking in safety and survival. The most common cost is the back pain.

Cognition: Larger brain.

• Feet is one of the human’s balance- keeping systems.
• The structure of the foot is similar to the structure of our hands.
• There is a web of muscles that help keep the balance.
• Feet tend to be almost totally flat; they have a small main arch in the internal middle section.
• Human feet have aligned toes, creating two arches.
• One distributes weight across the sole and other is a shock absorber.
• The design of the bones creates three arches on the foot. The medial arch, the lateral arch and fundamental longitudinal arch are created by the structure it takes.

• The brain has two sides: right and left hemispheres.
• Right Hemisphere: The right side of the brain controls the left side of the body, including muscles and sensations.
• Right Hemisphere: spatial abilities face recognition, visual imagery, and music.
• Left Hemisphere: The left side of the brain controls the right side of the body, again including muscles and sensations.
• Left Hemisphere: language, math, and logic.
• If a side of your brain is damaged it means the other side of the body is going to be affected.

• In 2007 a team led by Herman Pontzer, observed and experiment the energetic of chimpanzees. Bipedal walking organisms consume 75% less energy, measured in the oxygen consumption. With one slight increase in leg length and hip extension, a quadruped walker would save more energy if it walked bipedally. Energy savings might have led to the evolution of bipedalism in hominids; as Africa became drier and cooler, forest shrank, and locomotion on two legs would be the most effective way to travel to the lonely food locations.
• Bipedalism was the result of adaptation for survival, since food sources started to be separated from each other with great distances, transportation on two legs was faster, more effective and more energy saver.

• It is believed that bipedalism is the result of evolution for freeing our hands to carry valuable resources.
• In a study published in the journal Current Biology, the researchers went to the Republic of Guinea in West Africa. Here they provided piles of coula nuts and oil palm nuts to 11 chimpanzees. The chimpanzees preferred de coula nuts over the oil palm nuts. The coula nuts are rare in this area, and chimps were 4 times more likely to pick up the coula nuts and walk away walking on two legs. Plus the walking on two legs, the quantity of nuts increased twice as much when walking quadrupedally (meaning walking bipedally probably is more effective that quadrupedally). Researchers concluded that chimpanzees carried the valuable nuts to another location to avoid the competition with other chimps, and that walking bipedally was the best way to do it. They also observed crop-raiding chimps and noted that when they stole crops such as papayas they ran away on two legs. Researcher believed that the same case would occur with early hominids. In conclusion bipedalism is effective and the best way of locomotion.

• The “three C’s”: cognition, culture, and cooperation.
• Cognition: the development of a larger brain can be represented by artifacts such as stone tools and weapons that signify better abilities for innovation and thinking said a paleoanthropologist and archaeologist from Stony Brook University.
• Culture: an oversized brain led to culture, as a result of thinking and social learning through language, creativity and innovation also affected. “In the wild, a lone human would not be able to survive without culture, explained evolutionary theorist Rob Boyd of University of California, Los Angeles.”Think about what is necessary to live in Alaska," he said. "You’d need a kayak, a harpoon, a float to not sink. Nobody invents a kayak. People learn the proper way to make a kayak from others." Additionally, Boyd said culture gives humans a survival advantage that is beyond the capacity of other animals. "Typical apes live in a particular habitat. We can make the changes on timescales that are very fast," he said.”
• Cooperation: humans gained a lot from cooperation, whether it was haunting or migration, humans with culture shared the same goals. Through cooperation humans would gain a better survival, colonization and an increase in reproduction. Joan Silk of the University of California, Los Angeles is an anthropologist that once said that primates also cooperate, and even that some primates breeding is stress-relieving, which gives a greater reproductive success.
• Incredibly large quantity of neurons in our brain.

• The femur supports most of the body weight, that’s why it is so thick and strong.
• Long thigh bones create the ability to take longer strides, therefore you can walk farther and faster.
• Connection between hip bones and upper leg is long. The base is strong and is capable to withstand the stresses of running and walking. Also allow us to walk upright.
• Strong knees help support our body's weight while we are walking.

Culture: Thinking and social interaction.

Cooperation: Culture and sharing goals; creating a bond.

You Got Some Nerve

All Brains On Board

Bon Apetit

You Got Some Nerve

Bon Apetit

• Neurons consume a lot of energy.
• If apes are bigger why they don’t have more neurons? It is difficult to get enough energy for a big body and for that many neurons.

• It is better to rely on 5 senses than in 1 or 2 hyper-sensitive senses because we can gain more information, a better perspective, from an area or the place you are while 1 or 2 hyper-sensitive senses can give you a detailed information of 1 or 2 aspects of the place.

• Synapses: Information from one neuron flows to another neuron across a synapse. It contains a small space separating neurons. The synapse consists of:
• A presynaptic ending that contains neurotransmitters, the mitochondria and other cell organelles.
• A postsynaptic ending that contains receptor sites for neurotransmitters.
• A synaptic cleft or space between the presynaptic and postsynaptic endings.

• When we cook food, we break it down so it is easier to digest and, have more Kcal (energy) when it is cooked than when we eat it raw. Digestion will take less energy and more Kcal consumed means less time spent eating and more energy for less.

• A neuron is a basic processing unit.
• Each neuron receives electrical inputs from other neurons.
• The electrical discharges make nerve impulses.
• The structure of a neuron consists of a cell body called soma. The soma has multiple processes. There are two types of processes. Dendrites are highly branched processes that carry incoming information in electrical impulses (To the soma). Axons communicate cells with each other, they vary the length depend the distance that is between cells. The axon usually is surrounded with a fatty substance called myelin. Myelin is an action potentializer to propagate quickly from one cell to another, creating rapid signal transmission. The absence of this substance is critical.

• The cells differ from the neurons because the neurons transmit information throughout the body.
• They communicate information in chemical and electrical forms.
• Sensory neurons: Carry information from sensory receptor cells thru the body to the brain.
• Motor neurons: Transmit information from brain to muscles of the body.
• Interneuron’s: Responsible for communication between other neurons.
• The neuron has three basic parts, the dendrites, the cell body and the axon.
• “Some neurons have few dendrite branches, while others are highly branched in order to receive a great deal of information” (Cherry).
• “A neurotransmitter is a chemical messenger that carries, boosts and modulates signals between neurons and other cells in the body”(Cherry).
• Excitatory neurotransmitters: These types have excitatory effects on the neutron; it’s more likely that the neuron will fire an action potential. They include epinephrine and norephrine.
• Inhibitory neurotransmitters: Inhibitory effects on neuron, less likely that neuron will fire and action potential, they include serotonin and GABA(Gamma-Aminobutyric acid).

• “How did we get here, then? Well, if our brain costs just as much energy as it should, and if we can't spend every waking hour of the day feeding, then the only alternative, really, is to somehow get more energy out of the same foods. And remarkably, that matches exactly what our ancestors are believed to have invented one and a half million years ago, when they invented cooking. To cook is to use fire to pre-digest foods outside of your body. Cooked foods are softer, so they're easier to chew and to turn completely into mush in your mouth, so that allows them to be completely digested and absorbed in your gut, which makes them yield much more energy in much less time. So cooking frees time for us to do much more interesting things with our day and with our neurons than just thinking about food, looking for food, and gobbling down food all day long. So because of cooking, what once was a major liability, this large, dangerously expensive brain with a lot of neurons, could now become a major asset, now that we could both afford the energy for a lot of neurons and the time to do interesting things with them. So I think this explains why the human brain grew to become so large so fast in evolution, all of the while remaining just a primate brain. With this large brain now affordable by cooking, we went rapidly from raw foods to culture, agriculture, civilization, grocery stores, electricity, refrigerators, all of those things that nowadays allow us to get all the energy we need for the whole day in a single sitting at your favorite fast food joint. So what once was a solution now became the problem, and ironically, we look for the solution in raw food. So what is the human advantage? What is it that we have that no other animal has? My answer is that we have the largest number of neurons in the cerebral cortex, and I think that's the simplest explanation for our remarkable cognitive abilities. And what is it that we do that no other animal does, and which I believe was fundamental to allow us to reach that large, largest number of neurons in the cortex? In two words, we cook. No other animal cooks its food. Only humans do. And I think that's how we got to become human” (Suzana Herculano).

• The cerebrum weighs about 2 pounds.
• The cerebrum contains billions of neurons that control everything that a person does, thinks, and the senses.
• The cerebrum controls language, senses, thinking and personality.
• The cerebrum is the largest part of the brain, which is divided into 4 lobes. The cerebrum is also divided into 2 parts that are linked by the corpus callosum. Corpus callosum passes messages between the two sides of the brain.
• The four lobes of the cerebrum are the frontal, parietal, temporal and occipital lobes.
• The cerebrum is involved in intellectual functions such as memory, attention, awareness, thought, language, and consciousness.
• The cerebrum has two layers. a thick layer named cerebral cortex A.K.A. “gray matter”. This layer is involved with thinking, coordination of movement and personality.
• The second layer is the white matter. It is a network of fibers that allow different parts of the brain to communicate.

So Childish

Bon Apetit

• When we cook food, fire predigests it for us.
• Predigested food means less energy spent in digestion.
• Less energy spent in digestion means less energy required for survival.

• A longer childhood seems to be an adaptation.
• In a longer childhood kids have a greater development. During childhood we learn culture, language and in general we learn things faster.
• In our childhood we learn about ourselves and society.

• During our childhood we learn language.
• We learn language by hearing our parents talking.
• During childhood we learn faster, so if we have a longer childhood we learn more during a longer period of time.

• Behavioral flexibility is the ability to perform and invent new behaviors.
• Complex societies make easier the process to pass information down from one generation to the next.
• During childhood we learn the culture to depth since in this humans tend to learn faster.

Increase in neurons

Developed brain

Free hands

Nervous system

Tools

Walking upright

Cooking food

Background

“An American Monkey after getting drunk on Brandy would never touch it again, and thus is much wiser than most men" - Charles Darwin

“It is not the strongest of the species that survive, nor the most intelligent, but the most responsive to change”

-Charles Darwin

• Evolution is the series of adaptations throughout time.
• Change throughout time in physical traits/features of a living organism occurs because of the ability of adaptation and natural selection.
• There are two mechanisms of evolution: natural selection and genetic drift.
• Humans are living organisms, such like animals and plants, with extraordinary abilities.
• Remarkable changes throughout time.

Complex culture

• Our hands are different from the hands of the rest of the animals in the human kingdom because we have a FULLY opposable thumb, with proportional size of the fingers with the hands plus the opposable thumb permits us to have the precision grip (a grip for the effective use of tools) that other animals don't have.
• Bipedalism allowed us to free our hands and give them other uses such as to carry reliable sources and use it with tools; walking on two legs helped to save more energy because less things are moving while we are walking and walking upright stretches our digestive system making the digestion faster and consuming less energy; although walking upright it is not simple because many factors are affecting it (spine and feet for example).
• The human brain is not the largest in size but surely is the number one in quantity of neurons, neurons basically control our intelligence and our brains capacity; the brain has a very complex structure but it can be divided into two sides: left hemisphere and the right hemisphere.
• We as humans have a nervous systems, where neurons are the basic processing unit, is the basis of our nervous system; plus we rely our information on 5 senses which are better than 1 or 2 hyper-sensitive senses since we gain more information about the place.
• We are the only animals that cook our food, cooking food means that fire breaks down the food for our body and this way we gain more energy for less quantity of food.
• A longer childhood means a larger period of time of learning things, and faster, and during this time of our lives we learn about our complex culture, in other words we learn about the world and what is living in this planet.

Evolution has created many adaptations opening us, humans, the path to be what we are today (the power as a living organism we have (Design of our body)) and to be the dominant specie in the whole world; there are 6 main factors that make us humans: our hands, walking upright, our brain, our nervous system, cooking food and having a longer childhood.

“In the long history of humankind those who learned to collaborate and improvise more effectively have prevailed”

- Charles Darwin

Longer childhood