1. Common Misconceptions About Evolution

2. #1: Isn’t evolution just a theory that even scientists can’t agree on?

3. First we need to look at what the word theory means. The Oxford English Dictionary gives two meanings: Theory, Definition 1: Theory, Definition 1: A scheme or system of ideas or statements held as an explanation or account of a group of facts or phenomena; a hypothesis that has been confirmed or established by observation or experiment, and is propounded or accepted as accounting for the known facts; a statement of what are held to be the general laws, principles, or causes of something known or observed.

4. #1: Isn’t evolution just a theory that even scientists can’t agree on? Theory, Definition 2: Theory, Definition 2: A hypothesis proposed as an explanation; hence, a mere hypothesis, speculation, conjecture; an idea or set of ideas about something; an individual view or notion.

5. #1: Isn’t evolution just a theory that even scientists can’t agree on? Darwin’s Theory, as with all scientific theories follow the first definition. Having your explanation for a group of observations being called a theory is an honor in the scientific field; it means that it is the best explanation we have for why something happens.

6. #1: Isn’t evolution just a theory that even scientists can’t agree on? Does being a scientific law mean you have more evidence to support your explanation than a theory? Not at all… laws and theories are used to describe different things in science.

7. #1: Isn’t evolution just a theory that even scientists can’t agree on? Scientific Laws describe what is happening. Examples include: Newton’s Laws of Gravity, Kepler’s Laws of Planetary Motion, Law of Conservation of Energy, Laws of Thermodynamics…. Scientific Theories explain why something happens. Examples include: The Big Bang Theory, Cell Theory, Theory of Relativity, String Theory…

9. #2: Was one of my ancestors really a chimpanzee?

10. NO! Evolution points to humans sharing a common ancestor with chimpanzees and other great apes around 7-8 million years ago. Chimps have continued to evolved alongside us since then. Sahelanthropus tchadensis Chimps are more like our cousins than our ancestors.

11. #2: Was one of my ancestors really a chimpanzee? The ancestor you share between yourself and the chimpanzee at the zoo probably did look something like this though: Sahelanthropus tchadensis

12. #2: Was one of my ancestors really a chimpanzee? We even shared the Earth at the same time with other hominid species such as Homo Neanderthalensis. And this recent find: Homo Floresiensis, the hobbit people on the island of Flores in Indonesia. In fact we have shared the Earth with many other human like species (called hominids). Courtesy of Smithsonian, 03/10

13. #3: How can natural selection lead to extremely complicated structures/organs like the human eye?

14. Though the eye is incredibly complex, even Darwin back in his day saw that the Theory of Evolution could account for it: “...if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real” -Charles Darwin, Origin of Species

15. #3: How can natural selection lead to extremely complicated structures/organs like the human eye? The first step in the evolution of the eye, would be a set of photoreceptor proteins that sense light called photoreceptors. Photoreceptors can sense ambient brightness, and distinguish light from dark. These allowed unicellular organisms to move toward where they sensed light, probably to use for photosynthesis. Example of a photoreceptor in a Euglena

16. #3: How can natural selection lead to extremely complicated structures/organs like the human eye? The next step would be indenting the tissue behind the eye to make a cup behind the photoreceptor cells. This enlarges the area of photoreceptor cells as well, now known as the retina. These primitive eyes are called eyespots. Example of an eyespot in a planarian (flat worm)

17. #3: How can natural selection lead to extremely complicated structures/organs like the human eye? The “pinhole camera” eye stage was next. This is where the eyespot hollows out more and reduces the size of the hole where the light comes through. This gave the organism true imaging, allowing for directional and shape sensing. Example of a pinhole eye in a nautilus.

18. #3: How can natural selection lead to extremely complicated structures/organs like the human eye? Next came eyes that were fully enclosed, fluid-filled chambers. A refractive lens has also evolved over the pin-hole. Refraction is when light waves change speed as they enter a new medium. This bends the angle of the light, and in the case of an eye (or camera) directs the light into a single beam on one spot. The refractive lens in most animals is known as the cornea. The iris later evolved, which allows the organism to adjust the “pin-hole”, controlling the amount of light that enters the eye.

19. #3: How can natural selection lead to extremely complicated structures/organs like the human eye? So if we remember that evolution is an accumulation of heritable changes, the evolution of complex structures like they eye, though remarkable, isn’t all that unrealistic.

20. #3: How can natural selection lead to extremely complicated structures/organs like the human eye? The eye is not perfectly “designed” either. If it was, it wouldn’t have what is known as the blind-spot.

21. #3: How can natural selection lead to extremely complicated structures/organs like the human eye? The eye is not perfectly “designed” either. If it was, it wouldn’t have what is known as the blind-spot.

22. “Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone on cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.” -Charles Darwin, On the Origin of Species