Exploring Hominid Evolution: Understanding Our Ancestry

Lab #2 Primate Evolution S24 Lab #2 Primate Evolution Introduction Now that you’ve seen how microevolution works, it’s time to explore macroevolution, the evolutionary changes that create new species. Our example of macroevolution will be – us! We will delve into the exciting and rapidly changing world of paleoanthropology, or the study of human/primate evolution. Humans are not descended from monkeys – this is a ridiculous statement. However, evolutionary theory holds that humans and apes share an ancient common ancestor who lived around 15-20 million years ago (MYA). As shown on the Hominid phylogenetic tree on page 17, the descendants of this modern ancestor spread and diversified, producing the modern species we find in the world today (including Homo sapiens ) and also producing some extinct lineages that can only be found in the fossil record. The task of a paleoanthropologist is to take all the data and try to recreate this pathway. This phylogenetic tree represents our “best estimate” as to how human evolution occurred based on the most current data, but this is a rapidly evolving field – every new fossil we find or every new test we run changes our understanding. We are still figuring out exact dates and branching patterns. For example, Homo ergaster fossils and Homo erectus fossils were thought to belong to two separate species when they were discovered in the 1950s, but new DNA evidence suggests they may actually be the same species. More data is needed to settle this question. We used to think that there was a single line of human evolution, with one species evolving after another until modern humans were reached. We now know this is not how humans evolved. The data shows that, like most other animals, we have a large and diverse family tree. There were periods in the past where three or four early human species lived at the same time, even in the same place. They may have interbred (for example, small amounts of Neanderthal DNA have been found in the genomes of people from Europe and Asia). Modern humans, Homo sapiens , are now the sole surviving species. Our closest living relatives are gorillas and chimpanzees, but there are some enormous differences between us and them. The fossils we are discovering from around the world are revealing lost species that bridge the gaps in our evolutionary history. The evidence supporting the hypothesized hominid evolutionary pathway is usually based on three types of analyses: Absolute and relative dating – Absolute dating uses the decay of radioactive isotopes (e.g. the C 13 used in Carbon dating) to determine the age of fossils, while relative dating determines their age in relation to fossils found in nearby (upper or lower) layers of rock. Molecular analysis – DNA can be harvested (in small amounts) from fossilized remains. This means we can compare DNA markers and sequences between different fossils and between fossils and modern species. The more similar the DNA sequences, the closer they should be on the evolutionary pathway. Morphological comparisons – This is the type of data we will focus on in the lab today. Morphology refers to an organism’s body shape – its bone structure, posture, wear patterns, etc. This data can tell us if an organism walked upright (was bipedal, or 2-legged instead of quadrupedal, or 4-legged), if it used tools, its diet, etc. Some of the characteristics of the skulls we will be comparing today are pictured below and described on the following pages: 1

Lab #2 Primate Evolution S24 2

Lab #2 Primate Evolution S24 Morphological features used to compare hominid skulls 3

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Lab #2 Primate Evolution S24 4

Lab #2 Primate Evolution S24 The following are all characteristics that have changed as humans have evolved: 1. Brain case a. Size – the bigger brain case allows for a bigger brain which, in general, means greater intelligence b. Presence of a pronounced brow ridge c. Forehead – size and height compared to face 2. Sagittal crest (also known as a cranial ridge ) and zygomatic arch a. Presence – if a sagittal crest is present, the organism has exceptionally strong jaw muscles, producing a powerful bite that can pierce flesh, break bone, and/or grind down tough, fibrous food. b. Size – the temporal muscles used in chewing attach to the sagittal crest, pass under the zygomatic arches (cheek bones), and connect to the mandible (lower jaw). Larger zygomatic arches allow larger muscles to pass through. The temporal muscles of a badger pass under its zygomatic arches 3. Snout a. Presence – a snout can block vision below the face, making it difficult to walk upright. b. Length – a reduced or shorter snout moves the molars (back teeth) under the rest of the skull, giving more flexibility in chewing and grinding food. This allows for a more varied diet. 4. Teeth a. Size – large molars (back teeth) with thick enamel are needed to grind tough, fibrous foods and to crack nuts. With this type of diet, there is not much need to cut through materials with incisors (front teeth), so they tend to be small. b. Canines – these pointed teeth can be large and sharp (to grab and slash meat and other animals) or they can be more like incisors (to bite soft food). 5. Foramen magnum (the hole in the base of the skull) a. Location – if at the bottom of the skull, it indicates the individual walked erect (bipedal), but if it is located at the rear of the skull it would have been easier to walk on 4 legs (quadrupedal). Pre-Lab Questions 5

Lab #2 Primate Evolution S24 1. What is the scientific name of humans (genus and species)? ____ homosapiens _______________________________ 2. What science studies hominid evolution? ___ paleoanthropology _______________________________________________ 3. What three types of data are used to determine hominid evolutionary relationships? ________________ ___ absolute and relative dating , molecular analysis, and morphological comparisons _ ___ ____ ___ __ 4. Are we absolutely sure the phylogenetic tree on page 5 is correct? ____No__________________________ 5. What is the name of the oldest species found on the phylogenetic tree? __ Sahelanthropus tchadensis 6. Approximately how many million years ago did humans and apes have a common ancestor? 15 million years _______ 7. Approximately how many million years ago did humans and Neanderthals have a common ancestor? __ ____ a little over 500,000 years ago ___ ____ ___ ____ ___ ____ ___ ____ ___ ____ ___ ____ 8. What does it indicated if the foramen magnum is located near the rear of a skull?_ Its quadrupedal _____________________________________________________________ 9. Where is a sagittal crest located? _____ the skull ________________________________________ 10. How is macroevolution different from microevolution?___ micro evolution refers to small changes over short time and macroevolution is large changes over a long period of time _________________________________________________________________________ 6

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Lab #2 Primate Evolution S24 Lab Procedures and Data Table #1: Ancient African Ancestors The oldest hominid fossils have been found in Africa . The ancient ancestor of apes and humans probably wandered through the jungles of this continent many millions of years ago. However, as the ecosystem in Africa changed from forest to grassland, swinging through the trees was replaced by walking on the ground. While some primates remained quadrupedal, our ancestors were figuring out how to walk upright. What are some advantages to being about to walk upright? ___ Walking upright not only allows us to see our predators and prey easily it conserves energy _______________________________________ __________________________________________________________________________________________ Compare the pictures on the following page to the skulls at this table. Use the skulls to label the images (this will greatly help you study and prepare for the lab practical!). Then, record an important fact of key characteristic about EACH skull using the space provided. Finally, answer the provided questions about these skulls. Name: Name: Gorilla Australopithecus afarensis “Lucy” Gorillas were predominantly herbivores Known to be the first direct decent of homo sapiens 7

Lab #2 Primate Evolution S24 Which of these skulls has a sagittal crest, what is its function? __ The gorilla_ ________________________ What is the oldest species represented on this table (it may not be a skull)? ___ Sahelanthropus tchadensis Which of these species is in the direct line of human descent? __ Lucy ______________________________________ Fill out the relevant rows of the table comparing skull characteristics on page 13. Name: Chimpanze Name: Australopithecus africanus The first chimpanzee was discovered in 2005 The first early human species with both human and ape like features 8

Lab #2 Primate Evolution S24 Table #2: Paranthropus species This lineage thrived for a while, but eventually all species in Genus Paranthropus went extinct (and we’re not sure why). While there are some similarities between these skulls and modern humans, these individuals were not our ancient ancestors. Again, use the skulls to label the images below, then record an important fact or key characteristic of each species. What feature do all of these skulls have in common? _ They are all apart of the Paranthropus species _____ What does this tell you about the diet of these species? ___ They had a varied diet and were able to chew for a long period_ _________________________________________ Name: Paranthropus robustus Name: Paranthropus boisei Robust was used to describe their tooth and face The last surviving Paranthropus They were found southern africa Name: Paranthropus aethiopicus Their massive jaws meant that they could chew for long periods of time 9

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Lab #2 Primate Evolution S24 Which of these species is the common ancestor of the other two? ___ Paranthropus aethiopicus __________ Do you think this species was bipedal or quadrupedal? Why? __ they are quadrupedal because the foramen magnum is located near the front of the skull ______________________________________ __________________________________________________________________________________________ The species on this table are the ones most closely related to modern humans. The earliest Homo fossils, Homo haibilis , are found in Africa, but these individuals spread across the globe as they evolved. The figure below shows how and when we think various Homo species migrated to different continents. 10

Lab #2 Primate Evolution S24 Timing and pattern of Homo sp. migrations 11

Lab #2 Primate Evolution S24 Use the skulls on this table to label the figures below and on the next page. Name: Mya Name: Parenthropus homo neanderthalensis The were found with complicated tools Our closest extinct relative The first species to wear clothing Name: Paranthropus Homo sapiens Name: Homo habilis The 1st early modern human The first hominid species to use tools 12

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Lab #2 Primate Evolution S24 Which of these species is the earliest/oldest? __ the earliest is homo Habilis and the oldest is homo heidelbegensis ___________________________________________________ Which of these species is most closely related to humans? __ Homo heidelbegensis_ _________________ Which of these species is not directly in the human evolutionary pathway (it’s a “dead end” offshoot)? _______ __ Homo neanderthalenis ________________________________________________________________ Which two of these species may actually be the same species?__ Homo dragster and Homo erectus ________ Examine the skulls of the two species you just identified. How are they similar? __ they have a similar ridge that protrudes at the top _______________________ __________________________________________________________________________________________ How are they different?_____________________________________________________________________ What do you think – are these the same or different species?_________________________________________ How can you support your answer? _____________________________________________________________ Fill out the relevant rows of the table comparing skull characteristics on page 13. Name: Homo erectus Name: Homo heidelbegensis This species was the first to leave Africa The common ancestor of humans and Neanderthals The cooked meat They hunted with spears 13

Lab #2 Primate Evolution S24 14

Lab #2 Primate Evolution S24 Table #4: Morphological Comparisons There is one specific table for this activity; instead, the data will come from all the skulls scattered across the room. As you work at each table, analyze the specific skulls listed below and record their characteristics in the chart. You only need to do this for the species listed below; you will N OT need to record this data on every skull. Morphological Comparisons of Primate and Hominid Skulls Tabl e N ame Brain Case (size and forehead) Sagittal Crest (present?) Zygomati c Arch (size) Brow Ridge Snout (size, length) Teeth Foramen Magnum (location) 1 Gorilla 1 Chimpanzee 1 Australopith ecus afarensis 2 Paranthropu s boisei 3 Homo habilis 3 Homo heidelbergen sis 3 Homo neanderthali s 3 Homo sapiens 15

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Lab #2 Primate Evolution S24 On the chart on the previous page: • Circle the names of the primates that are not involved in the evolution of hominids or humans. • Place a star by the hominids that did not continue to evolve into modern humans; i.e. by the “dead-end” lineages. Describe the trends you see observed in primate evolution from ancestral primate to modern man for each of the characteristics you have investigated. What may this mean to the development of modern man? Brain case Sagittal crest Zygomatic arch Brow ridge Snout Teeth Foramen magnum 16

Lab #2 Primate Evolution S24 Post-Lab Review Questions 1. Name TWO hominins we looked at today that are NOT our ancestors because they were evolutionary “dead ends.” (Note: gorillas and chimpanzees are not hominins)._____ Paranthropus aethiopicus and Homo neanderthalenis _________________________ 2. Which non- Homo sapiens species examined today is the closest relative to humans? ________________ ________ Australopithecus africanus ___________________________________________________ 3. What was the oldest species we looked at today? _____ Homo erectus ____________________ 4. What changes did you see in the size of the zygomatic arch in the species most closely related to humans? ____ It became smaller and less prominent ____________________________________ 5. Why? _____ This was evidence of a herbivore diet ____________________________________ 6. What changes did you see in the placement of the foramen magnum in the species most closely related to humans? _____ It went further down the skull _________________________________ 7. Which came first, Australopithecus afarensis or Homo habilis? ___ Australopithecus afarensis _____ 8. Which two fossils might or might not belong to the same species? _ Homo ergaster and Homo erectus _____________ 9. What was the first species to walk fully upright? __ Sahelanthropus tchadensis _________________ 10. What are some morphological differences between Homo sapiens and Homo neaderthalensis ?________ _ Homo neanderthalensis has bigger brow ridge and bigger eye sockets, brain case. 11. Distinguish between hominids and hominins. __ Hominins are all modern and extinct humans _____ ____________________________________________________________________________________ 12. What are the differences between apes and monkeys? ___ apes tend to be larger so they have a larger bone structure ________________________________ 13. How do fossil records aid in understanding primate evolution, and what insights have they provided? __ They are a direct example of our ancestors __________________________________________ 14. Determine from the diagram on page 5 how long ago the African ape’s ancestors and human ancestors split away__________ 6 million years ago_ __________________________________ 17

Lab #2 Primate Evolution S24 15. Explain the role of tool use in primate evolution. __This showed us not only increased motor functions but higher level brain activity__________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ 16. Reflection questions - using complete sentences , briefly describe ( at least a paragraph ) the following: Skipping this part or writing “one liners” will result in major points deductions. Main purpose and what you did in the Lab. What has been learned/observed 18

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Lab #2 Primate Evolution S24 17. References Brooker, Robert J., Eric P. Widmaier, Linda E. Graham, and Peter D. Stiling. (2014). The Vertebrates. Biology. 3 rd Edition, 684-714. Human Evolution Timeline Interactive. (2015, April 19). Retrieved August 21, 2015, from http:// humanorigins.si.edu/evidence/human-evolution-timeline-interactive . How can you use/ modify/apply this concept in real life? 19

Lab #2 Primate Evolutionn

Related Documents