From Archonta to Hominoids: a step-wise approach



Molecular phylogeny of the superorder Archonta: Adkins and Honeycutt

McGrawHill Higher Education, Introduction to Biological Evolution

Bringing Fossils to Life: an introductionto paleobiology by Donald R Prothero

Have put the sources upfront- am grateful to them.

The story of human evolution begins around 65 million years ago, with the explosive radiation (an evolutionary theory) of a group of small, arboreal mammals called the Archonta.

 (Radiation is commonly used to refer to a probable branching sequence as shown by anatomical analysis and molecular techniques)

They were insectivorous mammals had large eyes and were most likely nocturnal (active at night). Their radiation gave rise to different types of mammals, including bats, tree shrews, and primates, the order of mammals that contains humans.
While early primates were mostly insectivorous, their dentition began to change from the shearing, triangular-shaped molars specialized for insect eating to the more flattened, square-shaped molars and rodent-like incisors specialized for plant eating. Primates that evolved later also show a continuous reduction in snout length and number of teeth.

About 40 million years ago, the earliest primates split into two groups: the prosimians and the anthropoids. The prosimians (“before monkeys”) looked something like a cross between a squirrel and a cat and were common in North America, Europe, Asia, and Africa. Only a few prosimians survive today, lemurs, lorises and tarsiers . In addition to having grasping digits and binocular vision, prosimians have large eyes with increased visual acuity.

The anthropoids, or higher primates, include monkeys, apes, and humans. Anthropoids are almost all diurnal—that is, active during the day—feeding mainly on fruits and leaves. Evolution favored many changes in eye design, including color vision, that were adaptations to day-time foraging. An expanded brain governs the improved senses, with the braincase forming a larger portion of the head. Anthropoids, like the relatively few diurnal prosimians, live in groups with complex social interactions. In addition, the anthropoids like to care for their young for prolonged periods, allowing for a long childhood of learning and brain development.

The early anthropoids, now extinct, are thought to have evolved in Africa. Their direct descendants are a very successful group of primates, the monkeys. These are classified into- new world monkeys and old world monkeys.

The new world monkeys existed 30 million years ago. They all are arboreal, have flat spreading noses, and many of them grasp objects with long prehensile tails. Arthropoids that remained in Africa split into two lineages: one gave rise to the old world monkeys- and one gave rise to the hominoids about 25 million years ago.

For our research into the origin of communication, the African anthropoid lineage –the homoinoids, which includes the apes(gibbons, orangutans, gorillas and chimpanzees) and the hominids (humans and their direct ancestors) are critical.

We will explore hominoids and their acquisition of social consciousness and language, next.