Module 10 Flashcards
Hominids
The ancestral family that broke off from the other large-bodied hominoids (Pongidae family) and whose various ancestral species eventually gave rise to Homo Sapiens.
Shared derived characters of Hominids(that differentiate them from any other primate).
- Large brain size
- Complex tool-making behavior
- Bipedal Locomotion
Bipedality
Walking upright on two feet.
Possible reasons why hominids acquired bipedality as an adaption.
- Perhaps climate changes during the Miocene and into the Pliocene (7-5 million years ago) turned a lot of arboreal environments into swampy marshland where wading was necessary to get around and the hands were then freed up to carry things.
- Perhaps instead, environment became drier and arboreal areas became smaller and the land became more savanna-like with tall grasses, in which hominids would have had to go longer distances to find food.
- perhaps greater exploitation of food resources on the ground meant the need to carry more things increased.
Bipedality advantages
- It freed the hands for carrying objects and for making and using tools.
- Standing erect allowed for a “look-out” stance in order to watch for predators or prey over tall savanna grass.
- Standing erect provides effective cooling, allowing hominids to adopt activity patterns that permitted early hominids to range for food during midday and avoid competition with nocturnal predators and scavengers
- It is an efficient means of covering long distances, extending the feeding range of early hominids, giving greater access to varied food resources.
Morphological changes that allowed for efficient bipedalism in humans
- The ilium (the upper bone of the pelvis) is shortened top to bottom.
- The vertebral column has a forward curvature, which brings the center of support forward.
- The leg is elongated for a long, full stride and the knee has been modified to allow full extension of the joint.
- The femur is angled inward, keeping the legs directly under the body.
- The big toe is brought in line with the other toes and the foot arch helps absorb shock and push off with the foot.
Note: Bipedalism for early hominids was obligate and habitual +> meaning bipedal locomotion was shown by hominids the vast majority of the time.
Fossilization
The process through which organic materials eventually transform(over long periods of time) into a mineralized material. Fossils can include bones, shells, wood, and other traces of plants and animals.
Example: Life - Death - Sediment - time - fossilization - exposure.
Relative Dating
methods that put things in order, older to younger, without specifying dates in years.
Absolute Dating
Methods that provide ages in years (also known as chronometric dating).
Law of Superposition
The sequence of geological strata from bottom to top reflects the order of deposition from earliest to latest. Lower geological layers are older than layers closer to the surface.
Fluorine Dating
- Fluorine found in groundwater, absorbed by buried bones.
Radiocarbon (14C) Dating
- All living organisms absorb carbon
- Radioactive decay of 14C isotope
- Half-life of 14C is 5,730 years
- Identify the amount of 14C remaining in sample
- Calculate age of sample by using half-life
- Dates samples from 1940 AD to 50,000-70,000 years ago.
- Estimated with a range of error
Conclusion: Radiocarbon dating doesn’t work to prove evolution as it can’t go back that far in time.
Potassium-Argon(k/Ar) Dating
- Measures radioactive decay of 40K isotope
- 40K degrades into 40 Ar
- The ratio of trapped 40Ar to remaining 40K increases over time, allowing calculation of the time since the rock crystal solidified.
- Limited to dating solidified lava or volcanic ash.
- Half-life of 1.3 billion years
- Good technique for dating very old samples, from 2 million years ago to over 5 billion years ago.
