Skip to main content
Social Sci LibreTexts

5: Methods

  1. Last updated
  2. Save as PDF
  • Page ID
    299432

    • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

    \( \newcommand{\dsum}{\displaystyle\sum\limits} \)

    \( \newcommand{\dint}{\displaystyle\int\limits} \)

    \( \newcommand{\dlim}{\displaystyle\lim\limits} \)

    \( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

    ( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

    \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

    \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

    \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

    \( \newcommand{\Span}{\mathrm{span}}\)

    \( \newcommand{\id}{\mathrm{id}}\)

    \( \newcommand{\Span}{\mathrm{span}}\)

    \( \newcommand{\kernel}{\mathrm{null}\,}\)

    \( \newcommand{\range}{\mathrm{range}\,}\)

    \( \newcommand{\RealPart}{\mathrm{Re}}\)

    \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

    \( \newcommand{\Argument}{\mathrm{Arg}}\)

    \( \newcommand{\norm}[1]{\| #1 \|}\)

    \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

    \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    \( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

    \( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

    \( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vectorC}[1]{\textbf{#1}} \)

    \( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

    \( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

    \( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

    \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

    \(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)

    • How are human physical characteristics distinguished from other organisms:

      • Centered foramen magnum

      • V-shaped (parabolic) dental arcade; in non-human primates, it is U-shaped

      • Shorter, bowl-shaped pelvis

      • S-shaped vertebral column

      • Longer femur with bicondylar angle, larger and lighter femoral head

      • Arms shorter than legs

      • Non-grasping hallux (big toe)

      • Increased manual dexterity (thumb is longer)

      • Reduced prognathism (flatter face)

      • Reduction in size of dentition

    • Fossilization is a process that preserves remains or traces of a once-living organism

    • Ways fossilization can occur:

      • Organic material (remains) become mineralized

      • Organisms become trapped in tree resin that hardens after the tree is buried (amber-preserved fossils)

      • Freezing preserves remains

      • Tar pits or volcanic ash preserve remains

      • Imprints of animal tracks, shells, leaves, stems, or flowers become preserved

    • The first hominins (group consisting of modern humans, extinct human species, and all our immediate ancestors) originate in the African continent

    • Several fossils have been found in the Rift Valley region, and some have been found in Sterkfontein Valley (southern Africa)

    • The East African Rift Valley is a divergent plate boundary

      • The African and Nubian plates are drifting apart, and ocean is forming between the plates

      • Divergent plate boundaries have volcanic activity, so fossils are often better preserved in this region

      • The presence of volcanic activity means that certain types of radioactive dating methods can be used on specimens here

    • Sterkfontein Valley

      • There is no volcanic activity here, so radioactive dating methods cannot be used

      • Must use relative dating methods

    • Elements

      • Atomic # = # protons (same # of electrons)

      • Atomic weight = protons + neutrons

    • Nuclei with the same atomic number but different mass numbers are isotopes

      • Most elements have more than one stable isotope

    • Isotopes:

      • Stable isotopes - do not decay into another isotope

        • Ex: Both Carbon-12 and Carbon-13 are stable isotopes

      • Radioactive isotopes - decay into another isotope

        • Ex: Carbon-14 is a radioactive isotope

    • Radioactive decay

      • Unstable atomic nucleus loses energy by emitting ionizing particles and radiation -> transforms parent isotope into daughter isotope

    • Radiometric dating

      • Measures the abundance of a naturally occurring radioactive isotope within the  

      • material to the abundance of its decay products (constant rate of decay)

      • Isotopes – differ in the number of neutrons (some are unstable and decay over time: radioactive)

      • Parent isotope -> decays into daughter isotope

    • Carbon-14

      • Can date fossils up to 50,000 ya (years ago)

    • Potassium-argon

      • Can date fossils older than 50,000 ya

      • Use of volcanic rock (Rift Valley)

    • Argon-argon

      • useful for dating smaller samples and volcanic rock

      • greater accuracy than K/Ar for small samples

    • More info: https://humanorigins.si.edu/evidence/dating

    • Relative dating

      • Law of superposition; stratigraphy

      • Comparing unknown fossils with known species (method for chronologically ordering specimens)

    • Paleomagnetism

      • Positions of magnetic north and south poles are interchanged

      • There have been 183 reversals over the last 83 million years

        • Latest occurred 780,000 years ago. 

      • By analyzing magnetic properties, we can determine possible age of the specimen

    Photos:

    • See Google slides below:

    5: Methods is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

    1. Back to top
    • Was this article helpful?

    Recommended articles

    1. Article type
      Chapter
    2. Tags
      This page has no tags.