10.1 Analogies & Fossils

analogy in science

geology, archaeology, paleontology, astronomy, and all other natural history sciences (i.e. where we cannot directly observe the phenomena that created the record or data we observe) rely upon analogy to learn about the past

analogy in biology

investigating whether similarities (behavioral, anatomical, genetic) between two similar biological entities have a common origin (evolutionary history) and function (adaptation)

even reliance upon experimentation represents a form of analogy

assuming that causes of your results are representative of the causes of the similar results you could not examine first hand

analogy in human paleontology

functional anatomy - which we rely upon heavily to interpret the fossil record - is a form of analogy

(bonus) fossilization is…

a process by which formerly living things slowly have their organic material (carbon-based molecules) replaced by minerals - depend on environment

“splitters”

individuals who tend to name a new fossil a new species

lumpers

individuals who consider lots of different fossil specimens to be all of the same species

in terms of radiometric techniques, what does half-life mean

the amount of time it takes a radioactive isotope to decay to half of its original amount over an experimentally determined amount of time

what is the half-life of Carbon-14?

5730 (± 40 years)

which radiometric technique is only useful on formerly living things?

Carbon-14

the upper limit using the traditional radiocarbon technique

about 40,000 ybp

theoretically, how far back can C-14 accelerator mass spectrometry date fossils?

about 100,000 ybp

in practice, how far back can C-14 accelerator mass spectrometry date fossils?

about 80,000 ybp

the only time Argon gas is found naturally

in very hot & high-pressure conditions (i.e. the Earth’s core)

Potassium-40 is found

only in volcanic or igneous kinds of materials

what is K/Ar dating practically used for

only for hominoid fossils on volcanic materials

the half-life of Potassium-40

1.31 billion years

which radiometric technique essentially has no upper limit?

K/Ar

which radiometric technique does have a lower limit?

K/Ar

what is the lower limit of the K/Ar technique?

100,000 ybp (cannot measure materials younger than this)

why does the K/Ar technique have a lower limit?

not enough Argon gas has accumulated in the materials