Gorillas found to live in ‘complex’ societies, suggesting deep roots of human social evolution

Gorillas have more complex social structures than previously thought, from lifetime bonds forged between distant relations, to «social tiers» with striking parallels to traditional human societies, according to a new study.

Gorillas found to live in 'complex' societies, suggesting deep roots of human social evolution
Young gorillas take a break from feeding to socialize
[Credit: Wildlife Conservation Society]

The findings suggest that the origins of our own social systems stretch back to the common ancestor of humans and gorillas, rather than arising from the «social brain» of hominins after diverging from other primates, say researchers.

Published in the journal Proceedings of the Royal Society B, the study used over six years of data from two research sites in the Republic of Congo, where scientists documented the social exchanges of hundreds of western lowland gorillas.

«Studying the social lives of gorillas can be tricky,» said lead author Dr Robin Morrison, a biological anthropologist from the University of Cambridge. «Gorillas spend most of their time in dense forest, and it can take years for them to habituate to humans.»

«Where forests open up into swampy clearings, gorillas gather to feed on the aquatic vegetation. Research teams set up monitoring platforms by these clearings and record the lives of gorillas from dawn to dusk over many years.»

Some data came from a project in the early 2000s, but most of the study’s observational data was collected from the Mbeli Bai clearing, run by the Wildlife Conservation Society, where scientists have recorded gorilla life stories for over 20 years.

Gorillas live in small family units — a dominant male and several females with offspring — or as solitary male «bachelors». Morrison, who has worked at Mbeli, used statistical algorithms to reveal patterns of interaction between family groups and individuals in the datasets.

By analysing the frequency and length of «associations», she found hitherto undetermined social layers. Beyond immediate family, there was a tier of regular interaction — an average of 13 gorillas — that maps closely to «dispersed extended family» in traditional human societies e.g. aunts; grandparents; cousins.

Beyond that, a further tier of association involved an average of 39 gorillas, similar to an «aggregated group» that spends time together without necessarily being closely related. «An analogy to early human populations might be a tribe or small settlement, like a village,» said Morrison.

Gorillas found to live in 'complex' societies, suggesting deep roots of human social evolution
Silverback males Dwayne and Sangha, the dominant males of two different western
gorilla groups feed peacefully together in Mbeli Bai forest clearing
[Credit: Wildlife Conservation Society]

Where dominant males («silverbacks») were half-siblings they were more likely to be in the same «tribe». But over 80% of the close associations detected were between more distantly related — or even apparently unrelated — silverbacks.

«Females spend time in multiple groups throughout their lives, making it possible for males not closely related to grow up in the same natal group, similar to step-brothers,» said Morrison. «The bonds that form may lead to these associations we see as adults.»

«If we think of these associations in a human-centric way, the time spent in each other’s company might be analogous to an old friendship,» she said.

Occasionally, when lots of young males «disperse» from their families at the same time but are not yet ready to strike out on their own, they form «all-male bachelor groups» for a while. The researchers suggest this could be another bond-forming period.

The team uncovered hints of an even higher social tier of «periodic aggregations», similar to an annual gathering or festival based around «fruiting events», although these are too infrequent to detect with certainty from this study’s data.

In fact, Morrison and colleagues argue that sporadic fruiting schedules of the gorillas’ preferred foods may be one reason why they — and consequently maybe we — evolved this «hierarchical social modularity».

«Western gorillas often move many kilometres a day to feed from a diverse range of plants that rarely and unpredictably produce fruit,» said Morrison. «This food is easier to find if they collaborate when foraging.»

«Gorillas spend a lot of their early life in the family group, helping to train them for foraging. Other long-term social bonds and networks would further aid cooperation and collective memory for tracking down food that’s hard to find.»

Gorillas found to live in 'complex' societies, suggesting deep roots of human social evolution
Three western gorilla groups (Conan, Morpheus and Zulu) mingle peacefully as they feed
at the Mbeli Bai clearing in the Nouabale-Ndoki National Park, Republic of Congo
 [Credit: Wildlife Conservation Society]

A small number of mammal species have a similar social structure to humans. These species also rely on «idiosyncratic» food sources — whether forest elephants hunting irregular fruitings, or the mercurial fish schools sought by dolphins — and all have spatial memory centres in their brain to rival those of humans.

Before now, the species on this short list were evolutionarily distant from humans. Our closest relatives, chimpanzees, live in small territorial groups with fluctuating alliances that are highly aggressive — often violent — with neighbours.

As such, one theory for human society is that it required the evolution of a particularly large and sophisticated «social brain» unique to the hominin lineage.

However, Morrison and colleagues say the addition of gorillas to this list suggests the simplest explanation may be that our social complexity evolved much earlier, and is instead merely absent from the chimpanzee lineage.

«The scaling ratio between each social tier in gorillas matches those observed not just in early human societies, but also baboons, toothed whales and elephants,» added Morrison, from Cambridge’s Department of Archaeology.

«While primate societies vary a lot between species, we can now see an underlying structure in gorillas that was likely present before our species diverged, one that fits surprisingly well as a model for human social evolution.»

«Our findings provide yet more evidence that these endangered animals are deeply intelligent and sophisticated, and that we humans are perhaps not quite as special as we might like to think.»

Source: University of Cambridge [July 09, 2019]



Giant Bugs Many types of bacteria are shaped like microscopic…

Giant Bugs

Many types of bacteria are shaped like microscopic balls or rods, like the ones on the left of this image. But break a gene called murA – which builds the stiff bacterial cell wall – and something strange starts to happen. Within 24 hours, the bugs have grown into bizarre giant cells (right) that look nothing like the neat rods that they normally resemble. Under most circumstances, having a faulty murA should be enough to kill the cells. But researchers have worked out a clever way of keeping them alive long enough to see its strange effects. Many antibiotics are designed to target parts of the cell wall, yet bacteria are increasingly evolving resistance to these life-saving therapies. By figuring out how these bugs survive without such an essential cell wall gene, scientists hope to find ways of combating antibiotic resistance or developing more effective new drugs in the future.

Written by Kat Arney

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Archaeologists uncover biblical town of Ziklag

Researchers from the Hebrew University in Jerusalem, the Israel Antiquities Authority and Macquarie University in Sydney, Australia, believe they have discovered the Philistine town near Kiryat Gat, immortalized in the Biblical narrative. Ziklag is mentioned multiple times in the Bible in relation to David (in 1 Samuel and 2 Samuel). According to the Biblical narrative, Achish, King of Gat, allowed David to find refuge in Ziklag while fleeing King Saul and from there David also departed to be anointed King in Hebron. According to scripture, Ziklag was also the scene of a dramatic event, in which the Amalekites, desert nomads, raided and burned the town taking women and children captive.

Archaeologists uncover biblical town of Ziklag
Aerial view of the Ziklag excavation site [Credit: Israel Antiquities Authority]

The excavation, which began in 2015 at the site of Khirbet a-Ra‘i in the Judaean foothills — between Kiryat Gat and Lachish, has proceeded in cooperation with Prof. Yosef Garfinkel, Head of the Institute of Archaeology at the Hebrew University in Jerusalem, Saar Ganor of the Israel Antiquities Authority and Dr. Kyle Keimer and Dr. Gil Davis of Macquarie University in Sydney, Australia. The excavation was funded by Joey Silver of Jerusalem, Aron Levy of New Jersey, and the Roth Family and Isaac Wakil both of Sydney. The excavation has been ongoing for seven seasons with large areas being exposed — approximately 1,000 sq.m., leading to this new identification for Ziklag.

Archaeologists uncover biblical town of Ziklag
The original Philistine settlement at Ziklag dates back to the 12th century BCE
[Credit: Israel Antiquities Authority]

The name Ziklag is unusual in the lexicon of names in the Land of Israel, since it is not local Canaanite-Semitic. It is a Philistine name, given to the town by an alien population of immigrants from the Aegean. Twelve different suggestions to identify Ziklag have been put forward, such as Tel Halif near Kibbutz Lahav, Tel Sera in the Western Negev, Tel Sheva, and others. However, according to the researchers, none of these sites produced continuous settlement which included both a Philistine settlement and a settlement from the era of King David. At Khirbet a-Ra‘i, however, features from both these populations have been found.

Archaeologists uncover biblical town of Ziklag
Archaeologist unearths ancient vessels [Credit: Israel Antiquities Authority]

Evidence of a settlement from the Philistine era has been found there, from the 12-11th centuries BC. Spacious, massive stone structures have been uncovered containing finds typical of the Philistine civilization. Additional finds are foundation deposits, including bowls and an oil lamp — offerings laid beneath the floors of the buildings out of a belief that these would bring good fortune in the construction. Stone and metal tools were also found. Similar finds from this era were discovered in the past in excavations in Ashdod, Ashkelon, Ekron and Gath—the cities of the Lords of the Philistines.

Archaeologists uncover biblical town of Ziklag
Jugs and vessels found at the archaeological dig [Credit: Israel Antiquities Authority]

Above the remains of the Philistine settlement was a rural settlement from the time of King David, from the early 10th century BC. This settlement came to an end in an intense fire that destroyed the buildings. Nearly one hundred complete pottery vessels were found in the various rooms. These vessels are identical to those found in the contemporary fortified Judaean city of Khirbet Qeiyafa—identified as biblical Sha‘arayim—in the Judaean foothills. Carbon 14 tests date the site at Khirbet a-Ra‘i to the time of King David.

Archaeologists uncover biblical town of Ziklag
Collection of jugs found at the archaological dig [Credit: Israel Antiquities Authority]

The great range of complete vessels is testimony to the interesting everyday life during the reign of King David. Large quantities of storage jars were found during the excavation- medium and large-which were used for storing oil and wine. Jugs and bowls were also found decorated in the style known as “red slipped and hand burnished,” typical to the period of King David.

Following a regional archaeological study in the Judaean foothills managed by Professors Garfinkel and Ganor, a picture of the region’s settlement in the early Monarchic era is emerging: the two sites — Ziklag and Sha‘arayim-are situated on the western frontier of the kingdom. They are both perched atop prominent hills, overlooking main routes passing between the Land of the Philistines and Judea: Khirbet Qeiyafa in the Elah Valley sits opposite Philistine Gath, and Khirbet a-Ra‘i, sits opposite Ashkelon. This geographic description is echoed in King David’s Lament, in which he mourns the death of King Saul and Jonathan in their battle against the Philistines: “Tell it not in Gath, publish it not in the streets of Ashkelon.”

Source: Israel Ministry of Foreign Affairs [July 09, 2019]