Human Evolution Hominid Evolution

Human Evolution Benchmarks Objectives SC.912.L15.1 Explain how the scientific theory of evolution is supported by the fossil record, comparative anatomy, embryology, biogeography, molecular biology, and observed evolutionary change. SC.912.L.15.10 Identify basic trends in hominid evolution from early ancestors 6 million years ago to modern humans. I will identify the basic trends in hominid evolution including brain size, jaw size, language, and manufacture of tools. I will analyze important structural features of a variety of hominid skulls, collect data by measuring and observing. I will use the data to describe evolutionary trends between fossil and living specimens.

Adaptive Radiation In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available and opens environmental niches Notice when the dinosaurs went extinct 65 MYBP (millions of years before present) the mammals (small little rodents that had to hide underground from the dinosaurs) diversified into all different types very rapidly in a geological time frame. Extinction of dinosaurs

WHAT IS A PRIMATE? A primate is a mammal that has: Flexible fingers and toes to grip Large thumbs and toes Ability to fully rotate arms at shoulder joint Binocular Vision Well developed cerebellum and cerebrum (How is this an adaption for the way we live? Why is this more important for a monkey to do this? What does this suggest about the human ancestor?)

How would we distinguish these organisms?

Primate Adaptations: Finger and Toes Primates share several adaptations, many of which are extremely useful for a life spent mainly in trees. Most primates have five flexible fingers that can curl around objects. Most also have flexible toes. An opposable thumb and big toe allow many primates to hold objects in their hands or feet. An opposable thumb stands out at an angle from the other fingers and can be bent toward them to grip and object. What is the evidence of evolution and a common ancestor for primates in the picture above?

Primate Adaptations: Shoulders Primate arms can rotate around a strong shoulder joint.

WHY IS BINOCULAR VISION IMPORTANT? Binocular Vision: The ability to combine visual images from both eyes, providing depth and a 3-dimensional view of the world. Cover your eye. How does your vision change? How does having binocular vision change the fitness of the primate? Picture of animals that have binocular vision vs monocular vision Does anyone have a clue why a primate would have binocular vision? Pic of monuclar vs binocular vision…horse vs primate Many primates have a flat face with eyes facing forward with overlapping fields of view. This facial structure gives primates excellent binocular vision. Binocular vision is the ability to merge visual images form both eyes, thereby providing depth perception and a three-dimensional vision. (Judges distance) Why would binocular vision be helpful if you were a lemur? The eyes of rats and squirrels are on the sides of their heads.

Well-Developed Cerebrum Enables primates to display more complex behaviors than many other mammals. Emphasis on learned behavior. Adoption of orphans. Warfare between rival troops. Notice angle of the skull Lots of folding allows a more complex brain to fit in the skull.

WHEN DID PRIMATES EVOLVE? Primates (we are part of this group) evolved from a common ancestor that lived 65 million years ago. Primate Evolution (Valdes’ Pic with dates)

How did Hominids Evolve How did Hominids Evolve? Cause and Effect– This is What Today’s Lab Will Focus On The skull, neck, spinal column, hip bones, and leg bones of early species changed shape in ways that enabled later species to walk upright. The evolution of bipedal, or two-footed, locomotion freed both hands to use and carry tools. Saved energy and allowed them to see predators and prey more easily. Hominids also evolved much larger brains. The use of tools allowed for jaw size to be reduced. Larger brains allowed for the development of language and manufacture of tools.

JAW and Brain/Skull SIZE Technology--stone tools--permitted our prehistoric ancestors to hunt, kill, and carve up for transport large animals. All of this was done via tools, alleviating the need for the typical carnivore adaptations--strong jaws, sharp teeth, claws, powerful muscles for mastication (chewing), etc. At the same time the jaw was getting smaller the brain/skull was getting larger. Is there a relationship? Ape early ancestor humans

Less protruding more vertical Tool and language ability increase Jaw smaller (smaller teeth/rounded jaw) Brain/Skull size Larger Evolutionary time Notice the Angle of the Skulls/face (dotted arrow) Less protruding more vertical

OPTIONAL SLIDES

A Rarity Among Fossils Early hominids left few fossil relative to other animals. Only individuals that died on the shores of a lake or swamp or that fell into a mud pit would be covered by sediment. Fossils formed 3-5 m.y.a. are embedded within rock formations deep in the ground. Once exposed, fossils are quickly destroyed by erosion. In 1871, Darwin predicted that Africa was the most likely place to find these fossils because the closest relatives of humans, gorillas and chimpanzees, lived in Africa.

Hominid Evolution Most paleontologists agree that the hominid fossil record includes at least these genera: Ardipithecus Australopithecus Paranthropus Kenyanthropus Homo As many as 20 separate species. This diverse group of hominid fossils covers roughly 6 million years. All these species are relative of modern humans, but not all of them are human ancestors.

Hominid Evolution Hominid evolution did not proceed by the simple straight-line transformation of one species into another.

Homo sapiens Origins Two theories as to the origin of our species abound. The multi-regional model suggests that modern humans evolved independently in several parts of the world from widely separated populations of Homo erectus. The out-of-Africa model proposes that modern humans evolved in Africa between 200,000 and 150,000 years ago, migrated out to colonize the world, and replaced the descendants of earlier hominid species. Most paleontologist agree that modern humans arose some 200,000 years ago in Africa.

Out of Africa, But Who and When? Fossil data and molecular evidence suggest that hominids left Africa in several waves. Many researchers claim that H. erectus was the first to leave Africa. By a million y.a., migrants from Africa had crossed Asia and reached China and Java, and populations of H. erectus were living in several places across Asia.

The Greatest Journey Ever Told