Shubins book was ultimately illuminating and informative. Although it could occasionally be dull, their were many highlighted intriguing genetic and anatomic relations between humans and our evolutionary ancestors, and these fascinating connections elaborating in detail upon our unified biological origin and what it means for us today ultimately made the book a worthwhile read.
Shubin elegantly explains how many, such as the ear, structures we possess today are simply adaptations and distortions of those possessed by our evolutionary decendants. He highlights the ear, for example, and how the stapes was actually an adaptation of the hypomandibula jaw bone in sea abiding creatures like sharks. He delivers an intuitive explication of the ear, explaining how the outer ear is a relatively new development of land dwelling mammals, responsible for ferrying ambient in the case of humans air vibrations to the middle ear, possessing a linkage of three bones, the stapes, malleus, and incus, which distort a jell like sac penetrated by hairs connected to nerve cells which not only relay sensory information to the brain interpreted as sounds but also are responsible for supplying information on the position and movement/velocity of the head. I was previously unaware of how the inner ear functioned to contribute the brains understanding of the heads locomotion/position,and I thought that ethanols disfiguration of the jell in your inner ear being responsible for the dizziness associated with drunkness amusing. I had also never noticed that reptiles and fish never actually had outer ears. Furthermore, I never thought of how the genes regulating the origination of distinct structures could have evolved from a single gene, such as is the case of Pax 6 and 2.The final chapter is devoted to summarizing our unified family tree with the plethora of life on earth, and how again, ultimately we are simply more complicated, modified distortions of primordial life in a lineage whose phenotypical implications is directly observable in the life around us;this life clearly containing the genetic and anatomical precursors to that which we operate today.
.Shubin elaborates on how simpler structures in sea dwelling creatures were modified and extrapolated to those we utilize today. In his commentary on the development of the ear, he mentions how we use three canals to detect acceleration because we live in three dimensions, and that more simple organisms, such as primordial fish, initially tracked their own acceleration with a single canal. Does this imply that primordial organisms perceived the world in a reduced number of spatial dimensions, or that they simply had a less sophisticated understanding of their exterior movement.
.The fundamental essence of evolutionary theory being that all organisms are connected in a spiraling genealogical tree branching throughout time from the emergence of single cellular life on earth, how are scientists certain that there could not have been multiple “first ancestors”, that is single celled organisms which spawned large segments of what is currently defined as an utterly interrelated unifying heritage among all life forms on earth. Furthermore, how could the descendants of a single organism at a particular point in space and time have been able to permeate the globe.If there was a mass emergence of single celled organisms far back in time, were their spawn able to exchange genetic information, and could that be why, if such an event ever occurred, biologists talk of a single first ancestor.