Arboreal Theory Explained


For evolutionary theories, changes in physical characteristics or social behaviors occur because of the adaptation to a change that is placed upon a species. The strongest survive, with strength being defined by the ability to adapt.

The arboreal theory describes the process of change that occurred for humanity’s primate ancestors. Introduced by FW Jones in 1916, the theory is that primates evolved from their ancestors because of their ability to adapt to arboreal life.

Arboreal is a reference to the ability of a primate to live in trees.

Why Would Primates Move into the Trees?

The transition into arboreal life for primates is believed to have occurred at the end of the Cenozoic Era. It’s often referred to as the “Age of Mammals” because numerous species dominated during this period of development. Large mammals, such as the basilosaurus and the paraceratheirum, would have taken much of the existing ground space, whether the continents were connected or not.

At the same time the large mammals began to dominate, the smaller dinosaurs and birds began to experience extinction-level events. This allowed for a niche in arboreal life to begin forming.

For smaller mammals trying to compete for resources with the larger creatures, moving into the trees would make sense. It would be a chance to establish their own habitat, away from the demands that large herds of much larger mammals would allow.

The Lack of a Fossil Record Creates Uncertainty

When looking at the history of the modern primate, there are several problems present that make it difficult to trace the lineage of the species. There are few fossil records that have been found. Our knowledge about continental drift is limited. Changes in biological diversity or geology could have varying levels of influence.

An example of this is the geological record of South America. Research suggests that the South American continent was once part of Africa. This means the fossil record could be separated or even lost because of continental movement.

Arboreal theory must therefore rely on three potential scenarios when looking at the modern primate.

  1. Primates from Africa crossed the Atlantic in some way and found their way to South America to establish a new colony species.
  2. Primates in the Americas gave rise to the modern species in a process that is separate from the African process.
  3. African primates emerged earlier than the current fossil record suggests, which means they could have crossed the Atlantic when it was smaller or when Africa and South America were still one land mass.

There is also the issue of the evolving primate that must be addressed. Primates may have an arboreal ancestry, but the rise of humanity seems to counter the process. At one stage, humanoids emerged from the forests and did not have a tail or extended limb proportions. That means as arboreal primates thrives, there must have been non-arboreal primates that were also thriving.

Otherwise, a group of arboreal primates counter-evolved in their habitat and that evolution forced them to climb down from the trees. That would seem to run counter to the evolutionary process, since both arboreal and non-arboreal primates thrive in the modern world.

The Important Components of Development in the Arboreal Theory

Several of the habits and traits of primates, including their modern descendants, is believed to have developed by their time spent living in trees. This includes several physical traits that can even be found in humanity.

  • The ability to rely on sight instead of smell, even when a fight-or-flight mechanism is required.
  • The development of depth perception that allows for accurate and rapid movement.
  • The development of feet and hands that could grasp food, provide stability, or encourage movement.

Enhanced cognitive functioning was likely part of the evolutionary process as well. There was a need to process information rapidly, especially in an era where the animal population of the planet was rapidly dwindling, to carve out a niche for survival.

The original primates that adapted to the arboreal environment would survive because they had access to a unique food source. No other creatures could gather fruit while it was still on a tree. This meant the early primates had

Modern primates that still life an arboreal life spend much of their time crawling along tree branches. They reach for fruit. They eat with their hands. And, like their ancestors had to do, they continue to adapt. Primates have gone from being fruitarians to eating insects to stealing food from human marketplaces.

There’s just one issue that critics have with this idea: at one point in the earliest stages of this development, primates would have needed to thrive in the arboreal environment without any of the evolved traits. How could this be possible?

Survival of the Fittest Is How Natural Selection Works

Natural selection is the process where the fittest, strongest individuals can survive and then thrive in any given environment. It is an evolutionary process which affects every species on our planet.

In the earliest days of arboreal movement, many primates would have attempted to fill the niche that was available in the trees. Many would not have likely survived because they lacked the traits which would allow them to move safely, collect food, and avoid predators.

Those that had the talents and physical capabilities to make the arboreal transition would be able to carve out their own space on the evolutionary chain. They would have offspring that would retain the characteristics and abilities that allowed for survival.

As for the other primates that could not adapt, they would have likely moved back to the ground and established colonies of non-arboreal primates. From this action, we would receive a distinct separation between the species. This is how humanity could have emerged and why there are distinct tree-based primates in various species.

Survival of the fittest would take on a different meaning for primates as well. Because primates have fewer offspring, the goal of a family unit is to cultivate specific behaviors through protection, nurturing, and teaching. Each learned behavior is passed to the next generation, which allows for knowledge to continue doubling.

This means arboreal theory includes behavioral components that are incredibly complex, creating a distinctive quality: reproduction of the fittest.

The arboreal theory is just one potential explanation to describe how the modern mammal may have emerged. Because there is a lack of evidence in the fossil and geological records, there may never be a definitive fact-based answer that is provide for this part of our planetary history. What we do know is that primates were able to develop the skills necessary to remain arboreal, while others were able to develop the skills necessary to potentially evolve into the first humans.

We continue this evolutionary process today by passing our knowledge and traits to future generations.