106 - 11 online new

Wichita State University Name: _______________________ ANTH 106 Fall 2022 Tuesday/Thursday Instructor: Buchanan-Burke Lab 11 –The Genus Homo SECTION 3: The genus Homo Each fossil of a hominin represents a unique individual. Therefore, no two fossil hominins share identical morphologies. Morphological similarities can cluster fossils into the same species, but there is no rule regarding how similar fossils must be to each other to belong to the same species. Sometimes researchers disagree over whether a fossil represents a new species or belongs to a previously established species. This is especially difficult to determine because primates can have high degrees of sexual dimorphism. Males and females of the same species can look very different and establishing the sex of an individual from fossil remains can be very difficult. Therefore, a new fossil could represent the other sex of a species already established in the fossil record or a truly new species. Measures of variation (i.e., size and shape differences) can help determine whether a fossil’s morphology reasonably falls within the estimates of an existing species. In this lab, we will examine the morphological characteristics of each of the fossils and discuss the justifications for separating them into subsequent genera and species. Australopithecines Australopithecus afarensis – This is one of the oldest of the australopithecines. Australopithecus Afarensis lived between approximately 3.9 and 2.9 mya. Australopithecus exhibit post-orbital constriction that is greater than more recent hominins, but less than extant (still alive) hominoids. Australopithecus africanus – A. africanus was one of the first hominin ancestor fossils ever discovered, when in 1924 Raymond Dart excavated the Taung Child . A. africanus is remarkably similar to A. afarensis , yet we still prefer to keep them separate. Paranthropines Most of the Paranthropines were discovered in eastern Africa. The Paranthropines are known for their wide, ‘Dish-shaped’ face. This is a result of large temporal muscles (chewing muscles) that run underneath the zygomatic arches. The wide face shape combined with the robust, flat molars of the Paranthropines led to the hypothesis that Paranthropines ate mostly grasses and seeds. The sagittal crest is also a characteristic of the Paranthropines that is a result of the strong temporal muscles. Paranthropines have been classified into three species: P. aethiopicus (2.5 mya) , P. robustus (1.8-1.2 mya) , and P. boisei (2.3-1.2 mya). Early Homo

H. habilis is currently the oldest species included in the genus Homo (the oldest known specimens have been dated to ~2.4 million years ago). However, this taxon is controversial, because the specimens included within it exhibit a high degree of variation. It is not known whether these specimens truly all belong to H. habilis or whether the sample includes representatives of multiple species. Also, although H. habilis shares certain morphology, especially its limb proportions, are more similar to the earlier australopiths. Some researchers have even proposed that Australopithecus habilis is a more appropriate species name. Sagittal Crest 3.1 (5 pts) Do the morphologies between the Australopithecines and Paranthropines differ drastically? The Australopithecines had a more ape like cranial structure with smaller teeth, while the paranthropines had robust skulls and large teeth Post Orbital Constriction Sagittal Crest Face to Vault Ratio and Prognathism

In 1972 Eldredge and Gould took a look at the fossil record and noticed a trend. The trend was that there were major evolutionary changes that occurred in spurts in-between long spans of time. The theory was that evolutionary changes and development would occur rapidly and in spurts, and it was termed ‘Punctuated Equilibrium’. The other side of the argument is gradualism. Gradualism suggests that evolutionary changes occur gradually and slowly over long timespans. Microevolutionary changes occur at a very slow rate which slowly build up to a macroevolutionary change. 4.1 (5 pts) What are some of the problems regarding punctuated equilibrium when one looks at the fossil record? one of the problems reguarding the punctuated equilibrium would be the fossil record would be incomplete 4.2 (5 pts) Is gradualism a better or worse interpretation of the fossil record than punctuated equilibrium? Why? I believe it is better because the fossil record would be more complete. Along with a better transition in the fossil record. 4.3 (5 pts) Could punctuated equilibrium and gradualism be combined to form a new intermediate hypothesis? Explain why or why not. I do not believe they can be combined because to make them work you would have to take out key features in each Take-Home Assignment: Visit https://humanorigins.si.edu/evidence/human-fossils/mystery-skull-interactive

Identify Each of the Mystery Skulls and provide an explanation for how you correctly (or incorrectly) identified each fossil. 1. I thought the first skull was homo heidelbergensis due to the cheek bones 2. I was correct when I chose the Homo habilis because the wide skull 3. 4.