The Interdependence Hypothesis: How Human Evolution Evolved

Previous hypotheses:

(1) Big Mistake Hypothesis  --   collaboration evolved when humans lived in small groups. It is possible that collaboration had an advantage because it benefited kin and increased chances of reciprocity in the community. Reciprocity is critical because it determines an individual's reputation.

(2) Cultural Group Selection Hypothesis -- collaboration evolved in larger social groups. The hypothesis states that culture breads and individual's sense of altruism. The more altruistic a population is, the more successful it will be. Since humans tend to mimic one another, altruism becomes valorized by the community.

The Interdependence hypothesis is a new hypothesis of human evolution stating that at some point humans began to collaborate to survive and procreate. Collaboration first began in small populations and then spread to be a large societal norm.

When thinking about collaboration and altruism, people tend to use the prisoners dilemma as an example. However, there is also the "Stag Hunt Game," which states that individuals must collaborate with others to benefit; the benefits of collaboration are greater than those of any solo alternatives; and all solo alternatives must be forsaken in order to collaborate. Basically, if an individual can hunt a rabbit, but the group can hunt a deer (at the cost of losing the rabbit), then the group will collectively hunt the deer and have more food for the group. This is exhibited in human populations. It is not, however, exhibited in chimpanzees.

Since small communities benefited from working together, the community exhibited behaviors of altruism and collaboration. Once human populations began to grow and encounter other populations, collaboration allowed human sub-populations to better survive against increasing competition. Thus, collaboration was exhibited not only in individuals and small populations, but also in large communities and societies.

It is important to note that this explanation is a hypothesis, not a theory.

Source: http://americainclass.org/wp-content/uploads/2012/06/Tomasello-Michael-2012-Two-Key-Steps-in-the-Evolution-of-Human-Cooperation.pdf

http://www.eurekalert.org/pub_releases/2012-11/uocp-wit111612.php

Oxytocin Produces More Engaged Fathers and More Responsive Infants

A recent study shows that oxytocin administration to fathers increases their parental engagement, while their babies are more responsive. As we know, oxytocin is a neuropeptide that plays an important role in the formation of attachment bonds.The scientists in this study examined whether oxytocin administration in fathers had an effect on their engagement and connection with their child. However, the study also examined whether oxytocin effects on the parent's behavior would affect  physiological and behavioral processes in the infant.

The results showed that salivary oxytocin levels rose significantly in the fathers after oxytocin administration. Interestingly, infants showed similar increases in their oxytocin levels. Under the increased oxytocin condition, fathers showed increases in key parenting behaviors, such as touch and social reciprocity that fostered increases in infant social behavior, such as the social gaze and exploratory behavior.

These findings have important implications for the treatment of young children at risk for social difficulties. This insight may eliminate the need to administer drugs to young children in some cases.

http://www.sciencedaily.com/releases/2012/12/121210080639.htm

New Study Sheds Light On How Salmonella Spreads in the Body

Salmonella enterica is a major threat to public health. The disease is known to cause systemic diseases, such as Typhoid Fever, and gastroenteritis in humans and other animal species. The disease is acquired through oral ingestion of contaminated water or food and through contact with a carrier. Scientists at Cambridge wanted to find out how diseases such as Salmonella grow at the single-cell level and spread throughout the body.

During the infection, salmoellae are found in cells in the immune system, where they thrive and continue to grow. The bacteria adapt to their surroundings and inhibit the immune system cell's natural antimicrobial activity. These scientists discovered that the bacteria must also leave already-infected cells to spread to distant sites in the body. This exodus is necessary to combat escalating efforts by the local immune system. Ultimately, these scientists discovered certain genes and gene regions that play pivotal roles in the bacteria's ability to spread throughout the body. Their findings provide valuable knowledge that could help change the way we treat diseases.

http://www.sciencedaily.com/releases/2012/12/121206203411.htm

How Fins Became Limbs

Recent research suggests that hands and feet evolved from fins due to gains in DNA components that activate certain genes.

Researches added extra Hoxd13, a gene known to affect the forming of body parts, to the fin of a zebrafish embryo. The experimental embryo developed more cartilage and had reduced fin cartilage. This is consistent with the formation process of human limbs. As a result, the zebrafish developed one limb that appeared more like a leg than a fin.

After they confirmed that Hoxd13 is essential to limb development, the researches guessed that evolutions in control elements were responsible for increased expression of that gene. They introduced a Hoxd13 control element that is present in mice to the zebrafish. As they suspected, the control element had the ability to drive gene expression in mice.

http://www.sciencedaily.com/releases/2012/12/121210124521.htm

The Evolutionary Crime of Holding Algae Captive

Protozoa, apparently, "captured" algae millions of years ago, and used their genes for energy production. The result was a more powerful organism, which actually serves as the "missing link" in the evolutionary chain we have constructed today.

The genes of algae allowed protozoa to perform photosynthesis, and thus produce easy energy using sunlight. This was evidenced by frozen protozoa's dual nuclei cell structure, manifesting both its own and algae's.

The relationship with mutual, known as endosymbiosis, in which algae was literally living in the protozoa, and the sugars protozoa created through respiration were shared with the algae living inside of it.

Over millions of years, the organism eventually became one - the missing link in evolution.

http://www.eurekalert.org/pub_releases/2012-11/uom-ahc112812.php

The most harmful mutations in humans arose recently

A new study shows that over 86% of the most harmful mutations to humans actually arose only 5,000-10,000 years ago. 

These mutations are single nucleotide polymorphisms (SNPs), and while some of these are, as we know, not dangerous or sometimes even beneficial, they are more harmful than not.

Its posited that the Out-of-Africa Bottleneck led to an inefficient elimination of the most harmful mutations, rather than ridding our old genetic makeups of the harmful mutations. Furthermore, while these mutations existed before the bottleneck, they were essentially unseen or ineffective because of the large population of humans. The bottleneck diminished the human population to the point where the mutations became more manifest and more effective at affecting a significant portion of the population.

The study also found that "the older the genetic variant, the less likely it was to be deleterious." Additionally, about 81% of SNPs in Europeans and about 58% of SNPs in Africans arose in the past 5000 years. Older variants, from over 50,000 years ago were more frequent in Africans. These statistics serve as a testament to the out of Africa Bottleneck, and show how these harmful mutations became, essentially, more popular in the past 5,000-10,000 years.

http://www.eurekalert.org/pub_releases/2012-11/uow-mot112812.php

Social Cooperation and Punishment

A new study found how social cooperation may be linked to social exclusion through punishment.

Through punishment, cooperation may become more apparent and valued in society because organisms have an inherent proclivity against being excluded.

A present example of this is how drivers will have their licenses taken away if they drive under the influence, thus "excluding them from the driving community."

This model shows how, unlike past models, the punisher can be benefitted, which very easily links to the possibly transformation and relationship between punishment and social cooperation. Those who are not excluded feel more welcome, and also find more reason to remain within the group, because of the adverse effects of being excluded.

http://www.eurekalert.org/pub_releases/2012-12/iifa-ese_1120412.php