BI 140 Organismal Biology Prof. Sebastian Velez

Human Evolution Laboratory for BI 140

Human Evolution lab, Page �1

BI 140 Organismal Biology Prof. Sebastian Velez

Instructions: Read the text and look at the figures. Then answer the questions marked in bold in the online answer sheet posted on Blackboard.

All humans share a hominin common ancestor. We also share a common ancestor with all living primates. There are three groups of living primates:

1. Lemurs, lorises and pottos.

2. Tarsiers

3. Anthropoids, which includes monkeys and apes (humans are part of the apes).

The oldest known anthropoid fossils, about 45 million years old.

Question #1: Look at the phylogeny below. Which is more closely related to Anthropoids, Tarsiers, or Lemurs?

Question #2: Does the phylogeny say that “humans come from chimps”? If not, then based on the phylogeny, what can you say about the relationship between humans, chimps and gorillas?

Human Evolution lab, Page �2

BI 140 Organismal Biology Prof. Sebastian Velez

Most primates have hands and feet adapted for grasping, and flat nails. They also have skin ridges on fingertips (fingerprints in humans), large brains, short jaws, flat faces, forward-looking eyes, and have developed parental care and social behavior.

Question #3: What is the technical term used in class to describe a shared derived trait, such as the characters above?

Paleoanthropologists have discovered over 20 species of hominins.

Question #4: Looking at the illustration above, can you tell if the species appeared in a step-wise fashion, that is, one superseded the other, one at a time, or where some species contemporaries?

Australopiths are a paraphyletic assemblage of hominins living between 4 and 2 million years ago. Some species, such as Australopithecus afarensis walked fully

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BI 140 Organismal Biology Prof. Sebastian Velez

erect, but had small brains and are not considered as ‘modern humans’. Monkeys and apes have opposable thumbs. “Robust” australopiths had sturdy skulls and powerful jaws. “Gracile” australopiths were more slender and had lighter jaws.

Question #5: What do we mean when we say that Australopiths are a paraphytelic group?

The earliest fossils placed in our genus Homo are those of Homo habilis, ranging in age from about 2.4 to 1.6 million years. Stone tools have been found with H. habilis, giving this species its name, which means “handy man”.

Homo ergaster was the first fully bipedal, large-brained hominid. The species existed between 1.9 and 1.5 million years ago. Homo ergaster shows a significant decrease in sexual dimorphism (a size difference between sexes) compared with its ancestors. Homo ergaster fossils were previously assigned to Homo erectus; most paleoanthropologists now recognize them as separate species.

Homo erectus (pictured on the right) originated in Africa by 1.8 million years ago. It was the first hominin to leave Africa.

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Human Evolution lab, Page �4

BI 140 Organismal Biology Prof. Sebastian Velez

Neanderthals, Homo neanderthalensis, lived in Europe and the Near East from 350,000 to 28,000 years ago. They were thick-boned with a larger brain, they buried their dead, and they made hunting tools. Debate is ongoing about the extent to which genetic material was exchanged between neanderthals and Homo sapiens.

Look at the two competing hypothesis above, and answer the following question:

Question 6: What is the difference between the two hypothesis, in terms of the relationship between modern humans and neanderthals? The data supports the tree to the right. According to this phylogenetic hypothesis (the one on the right), are modern humans monophyletic, paraphyletic, or polyphyletic?

The oldest fossils of Homo sapiens outside Africa date back about 115,000 years and are from the Middle East. Humans first arrived in the New World sometime before 15,000 years ago. In 2004, 18,000-year-old fossils were found in Indonesia, and a new small hominin was named: Homo floresiensis.

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Human Evolution lab, Page �5

BI 140 Organismal Biology Prof. Sebastian Velez

Homo sapiens were the first group to show evidence of symbolic and sophisticated thought. In 2002, a 77,000-year-old artistic carving (pictured) was found in South Africa.

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