The first people to arrive in America traveled as at least two separate groups to arrive in their new home at about the same time, according to new genetic evidence published online on January 8th in Current Biology, a Cell Press publication.

After the Last Glacial Maximum some 15,000 to 17,000 years ago, one group entered North America from Beringia following the ice-free Pacific coastline, while another traversed an open land corridor between two ice sheets to arrive directly into the region east of the Rocky Mountains.  (Beringia is the landmass that connected northeast Siberia to Alaska during the last ice age.)  Those first Americans later gave rise to almost all modern Native American groups of North, Central, and South America, with the important exceptions of the Na-Dene and the Eskimos-Aleuts of northern North America, the researchers said.

” Recent data based on archeological evidence and environmental records suggest that humans entered the Americas from Beringia as early as 15,000 years ago, and the dispersal occurred along the deglaciated Pacific coastline,” said Antonio Torroni of Università di Pavia, Italy.  “Our study now reveals a novel alternative scenario: Two almost concomitant paths of migration, both from Beringia about 15,000 to 17,000 years ago, led to the dispersal of Paleo-Indians—the first Americans.”

Such a dual origin for Paleo-Indians has major implications for all disciplines involved in Native American studies, he said.  For instance, it implies that there is no compelling reason to presume that a single language family was carried along with the first migrants.

When Columbus reached the Americas in 1492, Native American occupation stretched from the Bering Strait to Tierra del Fuego, Torroni explained.  Those native populations encompassed extraordinary linguistic and cultural diversity, which has fueled extensive debate among experts over their interrelationships and origins.

Recently, molecular genetics, together with archaeology and linguistics, has begun to provide some insights.  In the new study, Ugo Perego and Alessandro Achilli of Torroni’s team analyzed mitochondrial DNA from two rare haplogroups, meaning mitochondrial types that share a common maternal ancestor.  Mitochondria are cellular components with their own DNA that allow scientists to trace ancestry and migration because they are passed on directly from mother to child over generations.

Their results show that the haplogroup called D4h3 spread from Beringia into the Americas along the Pacific coastal route, rapidly reaching Tierra del Fuego.  The other haplogroup, X2a, spread at about the same time through the ice-free corridor between the Laurentide and Cordilleran Ice Sheets and remained restricted to North America.

” A dual origin for the first Americans is a striking novelty from the genetic point of view and makes plausible a scenario positing that within a rather short period of time, there may have been several entries into the Americas from a dynamically changing Beringian source,” the researchers concluded.

Researchers have revealed the complete mitochondrial genome of one of the world’s most celebrated mummies, known as the Tyrolean Iceman or Ötzi.  The sequence represents the oldest complete DNA sequence of modern humans’ mitochondria, according to the report published online on October 30th in Current Biology, a Cell Press publication.

Mitochondria are subcellular organelles that generate all of the body’s energy and house their own DNA, which is passed down from mother to child each generation.  Mitochondrial DNA thus offers a window into our evolutionary past.

“Through the analysis of a complete mitochondrial genome in a particularly well-preserved human, we have obtained evidence of a significant genetic difference between present-day Europeans and a representative prehistoric human—despite the fact that the Iceman is not so old—just about 5,000 years,” said Franco Rollo of the University of Camerino in Italy.

The Tyrolean Iceman witnessed the Neolithic-Copper Age transition in Central Europe more than 5,000 years ago.  His mummified corpse was recovered from an Alpine glacier on the Austro-Italian border in 1991.  In 2000, scientists defrosted the Iceman’s body for the first time and sampled DNA from his intestines.

Earlier study of the DNA showed that he belonged to the lineage, or “subhaplogroup,” known as K1.  About 8% of modern Europeans belong to the K haplogroup, meaning that they share a common ancestor, and that group is divided into two “subhaplogroups,” K1 and K2.  The K1 haplogroup, in turn, can be divided into three clusters.

In the new study, the researchers took advantage of advanced genome-sequencing technologies to shed more light on the Iceman’s genetics.  They sequenced his entire mitochondrial genome and compared that sequence to other published human mitochondrial DNA sequences to construct his evolutionary (or phylogenetic) family tree.

“The surprise came when we found that the lineage of the Iceman did not fit any of the three known K1 clusters,” Rollo said.  His team has informally named the newly discovered branch on the human family tree “Ötzi’s branch.”

“This doesn’t simply mean that Ötzi had some ‘personal’ mutations making him different from the others but that, in the past, there was a group—a branch of the phylogenetic tree—of men and women sharing the same mitochondrial DNA,” Rollo said.  “Apparently, this genetic group is no longer present.  We don’t know whether it is extinct or it has become extremely rare.”

At least for the moment, he said, that means no one can claim to be “the issue of Ötzi.”

Although anthropologists and evolutionary biologists are still debating this question, a new study, published in the open-access journal PloS ONE, supports the view that the first egalitarian societies may have appeared tens of thousands of years before the French Revolution, Marx, and Lenin.  These societies emerged rapidly through intense power struggle and their origin had dramatic implications for humanity.  In many mammals living in groups, including hyenas, meerkats, and dolphins, group members form coalitions and alliances that allow them to increase their dominance status and their access to mates and other resources.  Alliances are especially common in great apes, some of whom have very intense social life, where they are constantly engaged in a political maneuvering as vividly described in Frans de Waal’s “Chimpanzee politics”.

In spite of this, the great apes’ societies are very hierarchical with each animal occupying a particular place in the existing dominance hierarchy.  A major function of coalitions in apes is to maintain or change the dominance ranking.  When an alpha male is well established, he usually can intimidate any hostile coalition or the entire community.

In sharp contrast, most known hunter-gatherer societies are egalitarian.  Their weak leaders merely assist a consensus-seeking process when the group needs to make decisions, but otherwise all main political actors behave as equal.  Some anthropologists argue that in egalitarian societies the pyramid of power is turned upside down with potential subordinates being able to express dominance over potential alpha-individuals by creating large, group-wide political alliance.

What were the reasons for such a drastic change in the group’s social organization during the origin of our own “uniquely unique” species?  Some evolutionary biologists theorize that at some point in the Pleistocene, humans reached a level of ecological dominance that dramatically transformed the natural selection landscape.  Instead of traditional “hostile forces of nature”, the competitive interactions among members of the same group became the most dominant evolutionary factor.  According to this still controversial view, known as the “social brain” or “Machiavellian intelligence” hypothesis, more intelligent individuals were able to take advantage of other members of their group, achieve higher social status, and leave more offspring who inherited their parent’s genes for larger brain size and intelligence.  As a result of this runaway process, the average brain size and intelligenc e were increasing across the whole human lineage.

Also increasing were the abilities to keep track of within-group social interactions, to remember friends and their allies and enemies, and to attract and use allies.  At some point, physically weaker members of the group started forming successful and stable large coalitions against strong individuals who otherwise would achieve alpha-status and usurp the majority of the crucial resources.  Eventually, an egalitarian society was established.  Although some of its components are well supported by data, this scenario remains highly controversial.  One reason is its complexity which makes it difficult to interpret the data and to intuit the consequences of interactions between multiple evolutionary, ecological, behavioral, and social factors acting simultaneously.  It is also tricky to evaluate relevant time-scales and figure out possible evolutionary dynamics.

A paper published in PloS ONE today makes steps towards answering these challenges.  The paper is co-authored by Sergey Gavrilets, a theoretical evolutionary biologist, and two computer scientists, Edgar Duenez-Guzman and Michael Vose, all from the University of Tennessee, Knoxville.

The researchers built a complex mathematical model describing the process of alliance formation which they then studied using analytical methods and large-scale numerical simulations.  The model focuses on a group of individuals who vary strongly in their fighting abilities.  If all conflicts were exclusively between pairs of individuals, a hierarchy would emerge with a few strongest individuals getting most of the resource.  However, there is also a tendency (very small initially) for individuals to interfere in an ongoing dyadic conflict thus biasing its outcome one way or another.  Positive outcomes of such interferences increase the affinities between individuals while negative outcomes decrease them.  Naturally, larger coalitions have higher probability of winning a conflict.

Gavrilets and colleagues identified conditions under which alliances can emerge in the group: increasing group size, growing awareness of ongoing conflicts, better abilities in attracting allies and building complex coalitions, and better memories of past events.

Most interestingly, the model shows that the shift from a group with no alliances to one or more alliances typically occurs suddenly, within several generations, in a phase-transition like fashion.  Even more surprisingly, under certain conditions (which include some cultural inheritance of social networks) a single alliance comprising all members of the group can emerge in which resources are divided evenly.  That is, the competition among non-equal individuals can paradoxically result in their eventual equality.

Gavrilets and colleagues argue that such an “egalitarian revolution” could also follow a change in the mating system that would increase father-son social bonds or an increase in fidelity of cultural inheritance of social networks.  Interestingly, the fact that mother-daughter social bonds are often very strong in apes suggests (everything else being the same) that females could more easily achieve egalitarian societies.

The model also highlights the importance of the presence of outsiders (or “scapegoats”) for stability of small alliances.  The researchers suggest that the establishment of a stable group-wide egalitarian alliance should create conditions promoting the origin of conscience, moralistic aggression, altruism, and other cultural norms favoring group interests over those of individuals.  Increasing within-group cohesion should also promote the group efficiency in between-group conflicts and intensify cultural group selection.

“Our language probably emerged to simplify the formation and improve the efficiency of coalitions and alliances,” says Gavrilets.  The scientists caution that one should be careful in applying their model to contemporary humans (whether members of modern societies or hunter-gathers).  In contemporary humans, an individual’s decision to join coalitions is strongly affected by his/her estimates of costs, benefits, and risks associated as well as by cultural beliefs and traditions.  These are the factors explicitly left outside of the modeling framework.

In humans, a secondary transition from egalitarian societies to hierarchical states took place as the first civilizations were emerging.  How can it be understood in terms of the model discussed?  One can speculate that technological and cultural advances made the coalition size much less important in controlling the outcome of a conflict than the individuals’ ability to directly control and use resources (e.g. weapons, information, food) that strongly influence the outcomes of conflicts.

Nautiloids are the sole surviving family of externally-shelled cephalopods that thrived in the tropical oceans 450–150 million years ago. However, in the intervening years their modern soft bodied relatives dumped the shell and developed complex central nervous systems; which makes Nautilus ideally suited to discover the ‘evolutionary pathways that led to the development of the complex coleoid [soft bodied cephalopod] brains’ say Robyn Crook and Jennifer Basil. Knowing that the simple Nautilus brain lacks the structures required for memory in more sophisticated cephalopods, Crook and Basil decided to test the living fossil’s memory.

Training Nautilus pompilus to associate the smell of food with a blue light, the cephalopods eventually learned to respond to a flash of blue light by extending their tentacles. Then the scientists tested the cephalopods memories with a flash of light 3min, 30min, 1h, 6h, 12h and 24h after training. Amazingly, Nautilus remembered their training for up to an hour before the memory was lost, but then the memory returned 6h later, lasting up to 24h. Nautilus has both short and long term memory, just like modern cephalopods, despite lacking the same brain structures.

Crook and Basil are optimistic that the unsophisticated Nautilus brain could teach us how modern cephalopod brains evolved.