Evolution EvidenceOverview

By:

Historical Sciences –Reconstructing a Crime

• Discuss: When someone is accused of committing a crime, how are they shown to be guilty or not guilty?

• One thing we can not do is rewind time to repeat the crime.

• We can, however, use evidence to draw the most reasonable conclusion.

• We will use this same process used in a court room to determine if evolution is historically accurate.

Questions to Get You Thinking

• If evolution is true, what kind of evidence might you suspect you would find in nature?

• If evolution is false, what kind of evidence might you suspect you would find in nature?

• Is there any evidence to support the theory of evolution?

• If so, what kind of evidence?

Evidence Overview

• Similarities between species showing common ancestry

• Progressions of species changing over time• Remnants of past generations within species

Similarities – Family Resemblance

• Discuss: Do people ever say that you look like anyone else in your family? Why?

• In the same way that people in the same family look alike, so species that are related also share similarities inherited from common ancestors.

Examining the Evidence – Similarities

• What might disprove evolution: – species are totally unique, unlike each other.

• Strong evidence in support of evolution: – Similarities from multiple disciplines agree –

genetics, anatomy, behavior, geography, etc.– Species share greater number, intensity, and variety

of similarities the more recent they shared a common ancestor

– The similarities shared between species are arbitrary or harmful to have

Anatomical Similarity: 5 Fingers

• Vertebrates usually have a humerus, an ulna, a radius, wrist bones, and five fingers, even though they use them for very different purposes – walking, grasping, flying, swimming, digging, etc.

Anatomical Similarity: Neck Vertebrae

• Almost all mammals have 7 neck vertebrae, even though they use them very differently

Similarity: Orchid Structure

• Orchids of incredible variety have the same pattern of parts

Similarity: Number of Legs

• Though both groups are extremely diverse, insects have 6 legs, while arachnids have 8.

Arachnids Insects

Examples of Similarities Between Species

• Echinoderms, though very diverse, have 5 sides.

Biomolecular Similarities

• Species also share a number of molecular similarities.– Species share• the same genetic language• the same types of amino acids – L isomer• The same kind of sugars – D isomer Sugars

Amino acids

Genetic Language

Gene Similarities

• Humans share 98% of our genes with chimpanzees

• This picture graphically represents a comparison of one gene, FOXP2, shared by both humans and chimps. The white gaps are deletions or insertions that differ between humans and chimps. The red spots are significant genetic differences between humans and chimps. The letters that form the body of the chimp are the shared sequences.

Biogeographic Similarities

• Species that are related often come from the same area. This is even true for fossil species.– Almost all marsupials are in Australia – even fossil species– Lemurs are found only on Madagascar today

Progressions of Change –Putting the Frames of a Movie Together

• When we watch TV or a movie our brain puts together individual frames into smooth movements.

• Evolutionary progressions also come in similar "frame by frame" sequences.

Examining the Evidence –Progressions

• What might disprove evolution:– Species are shown to be unchangeable– Species remains do not show progressions of change

• Strong evidence in support of evolution– Modern dating techniques confirm the ages of fossils

within a progression– Multiple traits are held in common by evolving species

showing they are related– Multiple traits change over time within an evolving

species

Progressions

Examples of Progressions - Whales

• Modern day whales evolved from land dwelling relatives of hippos

Examples of Progressions - Whales• The back legs of the whales

become reduced over time• The nose of the whales

moves to the top of the head• As some whales transitioned

from eating with teeth to eating with baleen, some intermediate fossil species had both teeth and baleen – bottom right photo is of a

toothed whale with baleen blood vessels

Examples of Progressions - Horses

• Horses have evolved to become larger, have fewer toes, and to eat grass.

Examples of Progressions: Artificial Selection

• Dogs and wild mustard are excellent examples of how much a species can quickly be modified by selection.

Progressions Across Geography:Ring Species

• Ring species: As species spread across an area they sometimes wrap around geographic obstacles, like mountains, forming a ring. When the species meet on the far side of the mountain range, they can no longer reproduce together. They can, however, reproduce with the population that they most recently came from.

Remnants – Signs of Origins

• Coins minted in the U.S. have letters on them that tell which mint they came from.

• Discussion: Has anyone ever said that you have an accent? Do you think you do? What can we tell about where someone is from based on how they speak?

• Similar to the above signs of origins, we can look at species and tell a lot about their evolutionary history.

Remnants – Whale Legs

• Whales and dolphins have the vestigial legs early in development

• All whales and dolphins have the remains of hips and legs inside their body.

Remnants – Fibulas

• Horses have vestigial bones in their legs called fibulas.– These bones easily break

causing the horse great discomfort. Race horses have their legs wrapped to help prevent breaks.

• Many other species also have vestigial fibulas, chickens are one example.

• Discussion: Have you seen this bone while eating chicken?

Remnants in You!

• Coccyx• Wisdom teeth• Ear muscles• Goosebumps• Nictitating eye

membrane• Canine teeth

Genetic Remnants

• Pseudogenes are genes that no longer have their original function but are similar to functional genes.– Examples:

• humans can’t synthesize Vitamin C, but we possess the pseudogene to.

• 51% of human scent genes have mutated into pseudogenes

• Atavistic genes are genes are that are typically pseudogenes but occasionally mutate to be turned on again.– Examples

• Toothless chickens and baleen whales can grow teeth • Whales grow hind legs• Humans can grow tails

Thinking Evolutionarily

Knowing these patterns of evolution, you can now ask 3 very important questions about any species:

1. Does this species share any anatomical, geographic, or biomolecular similarities with any other species that are signs of their common ancestry?

2. Is this species a part of a progression of change seen in the fossil record, across geography, or in recorded history?

3. Does this species have any remnants of past generations within its anatomy or genome?