4. EmotionsHuman Genome

THE HUMAN EVOLUTION

Human Diversity Research about diversity in human groups,

made the last years, show that there are less genetic differences among humans that it was thought before

The color of skin, one of the most apparent differences, is controlled by a short number of genes that have no practical differences between the extremer cases

The total amount of melanin in humans is neither so different as it was waited before: in people with a clear skin melanin is disposed in deeper layers of the dermis

The wrongly called “races” are a set of adaptations acquired by the influence of climate and expressed in different external features of the body

That is why racial differences are basically external, but in a genetic level all human beings have very little differences and there may be more genetic differences between two Europeans than between Europeans and Africans, despite what the external appearance may suggest

Throughout history human species has been precisely characterized by the tendency to cross-breeding among humans from different origins, that is why the concept “race” has been questioned by most of the scientific community

Homo sapiens has one only origin and all human beings living now on earth come from the same ancestral trunk originated in Africa

There are more genetic similarities than differences among humans. Current human diversity has originated during the last 50 000 or 60 000 years

Populations emerged from Africa colonized south-east Asia and arrived in Australia and New Guinea some 60 000 years ago and in Europe some 40 000 years ago. The latest population belongs to north-east Asia and America, 35 000 years ago. Native settlers in South America come from Asia, as the similarities between these two human groups show

We are a “young” species, with a few genetic diversity (differences between two individuals < 1 %). Some 10 000 years ago sedentism started

MIGRATIONS OF HOMO SAPIENS SAPIENS

Features that make us different

1. Biological features shown at the picture are external and basically depend on evolutionary processes regarding climate. Then it is reasonable to expect external appearance differences between an African and a European

2. Instead of it, features that aren’t expressed externally, show less differences among human groups, due to our common origin and the great cross-breeding happened throughout history of mankind

Emotions make us human

What are emotions?

In 1884, psychologist Williams James proposed himself this very question in a celebrated assay where he introduced the definition:

“emotions are the result of perceiving changes in our body”

Identify and enumerate the emotions felt by the protagonist of the following story:

It’s 7 o’clock p.m. and you’re walking on the street while you’re writing absent-minded an SMS to a friend. You suddenly realize that you’re jumping backwards in the middle of the street while you hear the intense noise of a car horn and creaking brakes, then you see your mobile phone flying though the air and feel a tremendous fear. You stay sit down on the sidewalk step and feel so happy when you quickly guess that it’s been for short that you were not deeply hurt and the car that was running through the street has taken only some centimeters to knock you down. You’ve been so lucky! But happiness only takes a moment because you realize immediately that you’ve fallen on a dog’s shit and you get up with disgust. But that feeling doesn’t take too long because you can’t prevent an anger attack against yourself because of being so careless while walking on the street, so dangerous as it is. Your anger ends immediately as you see that, surprisingly, your mobile has been crashed by the car’s wheels, what arouses a feeling of sadness in you because it was just brand-new and it had taken you a long time to save the money to buy it

When we study emotions, a basic aspect is the controversy of including or not some related states. We refer to what is commonly known as feelings, including states like love, guilt or shame. Most people do not include feelings in the emotions catalogue because they consider they don’t fit to the features of an emotion like these:

1. They are mechanisms devoted to give urgent answers in our organism (prevent a danger, share our happiness, reject a wrong food). Actually, the word emotion comes from Latin movere, meaning “to move”

2. They are transitory mechanisms that contribute a value/interpretation to the experienced situation, in such a way to condition further individual’s attitudes (if some food has disagreed with us, we’ll prevent having it in the future)

What for and why we have emotions

As it always happens, according to the prevailing paradigm, we must search in our evolutionary past to find a reason that explains why do we feel sadness, happiness or disgust. Thanks to Darwin, who proposed the Theory of Evolution, we know that emotions, like almost everything produced by our brain, appeared and were inherited from one species to another because they made it possible to survive and reproduce those individuals that experimented them

Which functions did emotions fulfil?

Surviving in a world full of dangers requires that and an individual has mechanisms to answer quickly in order to change his behavior in the best efficient way as possible

Why did they have an adaptive value?

Fear should have the biological function of protecting us from danger, anger that of eliminating a competitor, happiness that of doing again what is being lived and is good, disgust to prevent damage, surprise to direct attention and sadness to make us value a lost

How do we acquire emotions each of us ?

During many years it’s been a matter to discuss whether emotions were innate or not, say, if we are born with them, or we acquire them during childhood. As far as we know until now, our brain seems to develop with a predisposition to experience some basic emotions: fear, anger, surprise, disgust, sadness and happiness. These emotions have been identified in almost every animal, they have been described in every human culture, they appear very early in babies’ development and each one is related to a particular physiological answer

It seems that these emotions automatically shoot in front of certain stimulus, like an intense noise, but the baby or child doesn’t learn this answer. Therefore, most of the situations whether we shall feel one emotion or another it will depend a lot on what the baby observes around it and the consequences of many of its personal experiences. We aren’t born with the innate predisposition to be happy when we pass a school test!

Several techniques to get a graphic representation of the

brain Magnetoencephalography (MEG)

X-ray computed tomography (CT scan)

Magnetic resonance imaging (MRI)

Positron emission tomography (PET)

Regional cerebral blood flow imaging with radioactive xenon (rCBF)

Some of these procedures allow us to find at which cerebral zones does blood flow while we do certain mental operations, what gives us a clue to track them down

MRI

MEG

CTscan

PET

rCBF

Cerebral circuits devoted to emotions

The new techniques used in neurology identify zones that are active in a given moment. As we do not use radiations and no substance must be injected, it is an innocuous and very precise advance to study the brain live. These advances have allowed us to track down which zones are activated when we feel these emotions. WE CAN CHECK IT ON THE NEXT TABLE...

Zones of Human Brain

The Amazing Story of Phineas Gage

Phineas P. Gage was born in1832. He worked as a foreman of a work gang blasting rock preparing the roadbed for a railroad and was a most appreciated and respected man by his relatives and friends. His heads were very proud of him, for he was an involved and responsible worker. On September 13, 1848, while he was using an iron rod in order to introduce dynamite into a hole, the powder exploded and the iron rod was projected and entered on the side of his face going out at the top of his head. Surprisingly, Phineas did not die, he did not even lose his conscience, even though most of his left frontal lobe was completely smashed…

…Some months after the accident, he went back to work but a few days later he was fired. His heads said he had become an irreverent and bad-mannered person. He didn’t show any sort of respect for people. He was now an uninhibited, capricious, impatient and childish person, with no capacity of planning or foreseeing the future...

Diagram of the Phineas Gage’s cerebral lesion

...His relatives and friends also realized the impressive change, and they even dared say that this person was not really Phineas. After the lesion in his frontal lobe, Phineas was no more the same person. The person in which he was transformed died on May 21, 1860. Seven years later, his body was exhumed and nowadays his skull and the iron rod that pierced it lay at the Warren Museum of the Medical College of Harvard University

Emotion and cognition

Although we have tried to relate each of the basic emotions to a specific cerebral structure, some of these regions are occupied in emotional processing and other are specialized in the cognitive processing, for example some specific zones at the frontal crust. Cognitive aspects allow us to modulate the intensity and expression of emotions. Our knowledge about the world gives us information regarding to whether it is appropriate or not laughing, or crying, etc. in certain situations

Information exchange between emotional and cognitive aspects can go in both ways. What means that emotions also modulate our cognitive faculties. For instance, that day being nervous in front of an examination paper that you became disappointed, although you had studied and knew your lessons perfectly. In that case, emotions had a negative influence and blockaded the regions devoted to cognition

Thanks to this interconnection between cognitive and emotional processes, we can apply psychological therapies, like the cognitive-conductive therapy, that can be beneficial to correct wrong attributions, like, for example, the depressive disorder. Some depressions are due to a bad functioning of the cingulated crust and those therapies help people to make an adequate analysis about the reason of their sadness and provide them strategies to overcome it

Human Genome

1988 : Several scientific teams all over the world start working in a coordinate way at the Human Genome Project

The aim was the knowledge of DNA sequences of all human chromosomes

Previously, scientists thought that human cells had some 100 000 genes. Human genome sequencing, published in 2001, has revealed that the 24 different human chromosomes (22 pairs, plus XX and XY) had only some 30 000 genes. Now they think there are between 20 000 and 25 000

As it seems there are huge regions with apparently no sense genetic information. Almost 95 % of human DNA is repetitive and near 35 % of the rest carries no information useful to synthesize any protein. It is named as junk-DNA, with huge “deserted” regions, without any genes, but having a very important regulating function

Some genes are fragmented and are hard to identify, besides there are evidences that 35 % of genes can be translated into proteins in cells in different ways

http://www.genome.gov/Students/

Molecular models for the DNA double helix : Calotte and ball-and-stick

THE GENETIC CODE

There are four nitrogenous bases: ADENINE,THYMINE GUANINE and CYTOSINE, that pair like this: A-T, G-C. The sequence of these bases at the DNA chain is read and translated into amino acids according to the upper table. Each triplet (codon) “means” an amino acid. U represents the base URACIL that substitutes thymine in mRNA. A gene is a base sequence with a meaning that can be translated

DNA in action: information contained in it is translated into mRNA (transcription) and moves out from the cellular nucleus to reach the ribosomes (translation) where protein chains are obtained with the help of tRNA

TRADICIONAL DOGMAOF BIOCHEMISTRY:

ONE GENE ONE PROTEIN

Now it is thought to be more complex

Advantages and risks of knowing the human

genome Knowledge and localization of human genes is very

important to biomedical sciences and has unpredictable consequences

This fact opens immense possibilities: to learn more about human evolution, to develop therapeutic strategies to fight and foresee genetic and hereditary illnesses (new medicines, genetic therapy)

But identifying the genome may also imply some dangers, like the anticipated identification of some illnesses and biological features that have not yet become apparent in individuals

There are genetic techniques that allow us to identify hereditary alterations, but we may fear that some detection tests could be used with the aim of discriminating some people (f.e., access to certain jobs, contracting health or life insurances, etc.)

We can also be concerned about human genome manipulation with non therapeutic purposes

Nevertheless, advantages that can be obtained from the application of this knowledge in fields like health, feeding and farming do amply better than the risks it implies

It is possibly one of the outmost scientific projects in history. To make an appropriate use and how do we apply it, is a responsibility to everybody

Our closest “relatives”

1. Hominids and chimpanzees’ lineages split in Africa some 6 million years ago; that’s why we have common ancestors with chimpanzees, but we are not descended from them

2. From a quantitative point of view (percentage of genetic differences), there are more differences between a man and a woman because we differ in a whole sexual chromosome: women have two X chromosomes while men have one X and one Y

3. The expression “to be more evolved” makes no sense at all, from a biological point of view. Evolution has followed different pathways depending on organisms and the environment where they were living. In some living things some features have had an extraordinary development while in others not. Dogs have a better sense of smell than us, giraffes have a longer neck and bats have an extraordinary hearing: which one is the “most evolved”?

To learn more ARSUAGA, J.L., MARTÍNEZ, I. La especie

elegida. Madrid: Ediciones Temas de Hoy, 2006.

CARBONELL, E. i BELLMUNT, C. Els somnis de l’evolució. Barcelona: La Magrana, 2003.

AUEL, J.M. El clan de l’ós de les cavernes. Barcelona: Columna, 1980.

GOULD, Stephen J. La vida maravillosa. Barcelona: Crítica, 2006.

http://www.atapuerca.org/

http://www.genome.gov/

http://www.ornl.gov/