Homology
Humans share a number of bone structures that are similar to other animals, which indicates that we share a common ancestor with other organisms. We have five different finger bones, just like bats and lions. These similarities show our connections, and also how we’ve diverged over time. By looking at fossils we can see how our different body parts have gradually evolved to become what they are today. Also, we have a number of body structures that have no clear purpose to our survival. However, they can be connected back to some of the more primitive ancestors. For example our tail bones are reminiscent of when we too had a tail. These functionless structures wouldn’t have another reason for existing, besides being “leftovers” from our past.
Many different pieces of evidence support the theory of human evolution. One kind of evidence is looking at human structures and how they can be linked to our transitional and ancestral figures. Some examples of these structural similarities are the facial bones and brain cavity among the many transitional phases. As time goes on we evolved to have a rounded open brain cavity and more of a vertical facial alignment. But the placement of these structures, shape, and functions stayed relatively the same.
![Picture](/uploads/4/7/9/7/47974937/9904455.png?498)
There are also similarities that aren’t completely skeletal based. The placement and function of many organs, bones, and structures in the face/skull are apparent in humans and their ancestors. The nasal cavity, soft/hard palates, and vocal chords are all examples. These support the theory of human evolution because through the transitional phases all the structures can be traced back.
![Picture](/uploads/4/7/9/7/47974937/387562.png?189)
Another example is the spine. As time went on our lumbar area of the lower back developed to make walking on two legs possible. The pelvic bones became more upright and wide allowing the spine to become more straight and flexible. This also allowed our legs to be placed more directly below/straight with the spine and pelvis. A piece of evidence that goes along with that is the development of the soles of the feet. As we evolved our heels became larger and made it easier to balance on two feet.
A vestigial structure is a body part or structure that has no current purpose or function but is still present in the organism.
- Appendix: Might have once helped our ancestors to digest cellulose in plant fibers
- Sinuses: Scientists cannot agree on a reason, but they’re not useful now
- Wisdom teeth: No longer fit in our mouths
- Tailbone: Was once a tail to help with balance
- Tonsils: Provided protection from pathogens we consume or breathe
- Group of muscles in ear: Would allow us to move our ears but most humans can’t anymore
- Arrector Pili (goosebumps)- Could provide insulation/warmth or make us look bigger to predators if we still had a lot of fur
- Male nipples: Not related to our ancestors, it’s because fetuses start their development as a female
- The palmar grasp reflex: Babies once may have needed to cling to their mothers as they were carried
- Plica semilunaris: Remnants of a nictitating membrane (3rd eyelid) that would help keep eyes clear/moist
“Appendix.” Remove Your Appendix through Your Mouth. N.p., n.d. Web. 26 Feb. 2015.
“Facial evolution.” Evolution of the Human Head. N.p., n.d. Web. 26 Feb. 2015.
“Pelvic evolution.” Pelvic Anatomy, Upright Posture and Health. N.p., n.d. Web. 26 Feb. 2015.
“Sinuses.” American Academy of Allergies Asthma and Immunology. N.p., n.d. Web. 26 Feb. 2015.
“Skull evolution.” BioNinja. N.p., n.d. Web. 26 Feb. 2015.
“Tailbone.” Brain and Spine Institute of California. N.p., n.d. Web. 26 Feb. 2015.
10 Vestigial Traits You Didn’t Know You Had. N.p., n.d. Web. 26 Feb. 2015.
“Tonsils.” Magnus Natural Remedies. N.p., n.d. Web. 26 Feb. 2015.
What Does it Mean to be Human. Smithsonian, n.d. Web. 26 Feb. 2015.
“Wisdom teeth.” Dentistry Altman. N.p., n.d. Web. 26 Feb. 2015.
Vestigial structures on humans. Slide Share. LinkedIn, 2015. Web. 27 Feb. 2015.
“Facial evolution.” Evolution of the Human Head. N.p., n.d. Web. 26 Feb. 2015.
“Pelvic evolution.” Pelvic Anatomy, Upright Posture and Health. N.p., n.d. Web. 26 Feb. 2015.
“Sinuses.” American Academy of Allergies Asthma and Immunology. N.p., n.d. Web. 26 Feb. 2015.
“Skull evolution.” BioNinja. N.p., n.d. Web. 26 Feb. 2015.
“Tailbone.” Brain and Spine Institute of California. N.p., n.d. Web. 26 Feb. 2015.
10 Vestigial Traits You Didn’t Know You Had. N.p., n.d. Web. 26 Feb. 2015.
“Tonsils.” Magnus Natural Remedies. N.p., n.d. Web. 26 Feb. 2015.
What Does it Mean to be Human. Smithsonian, n.d. Web. 26 Feb. 2015.
“Wisdom teeth.” Dentistry Altman. N.p., n.d. Web. 26 Feb. 2015.
Vestigial structures on humans. Slide Share. LinkedIn, 2015. Web. 27 Feb. 2015.