Reverse Evolution

The Devolution of Species

By: Ethan Woodside and Andrew Carenza

Reverse Evolution

DevolutionDefinition: the notion that a species can change into a more “primitive” form over time.

Also known as backwards evolution.

Reverse Evolution

A History of Devolution• Originally developed by Anton Dohrn as a theory of

degenerative evolution.• Degeneration: having reverted to a simpler form• States that according to environmental conditions some

chordates are degenerated.

Reverse Evolution

A History of Devolution• Paleontologist Alpheus Hyatt, believed certain animals

evolved up to a certain level but then started to regress back to previous evolutionary stages due to unfavorable conditions.

• He conducted this experiment using ammonoids (extinct mollusk species)– Ex. E.W. MacBride, a biologist, claimed invertebrates were actually

degenerate vertebrates, because crawling is less stimulating then swimming

Reverse Evolution

The Theory of Devolution• Devolution assumes evolution requires a purposeful objective

of moving towards increasing complexity.• Relies on the idea that some forms or structures of organisms

are more advanced than others.– Ex: A jaw is better than no jaw, feet are better than hooves and

increased stamina is better than decreased stamina.

Reverse Evolution

The Theory of Devolution• Thus devolution may revert from feet to hooves, or jaws to

jawless.• Could occur due to environment pressure causing the “less

advanced” trait to be advantageous.– Ex. modern horses; fossils of early horses show that they originally had

5 toes, and over time went to three and then finally one single toe or hoof.

– Caused by a change in their environment, where hooves were advantageous on plains, allowing greater speed.

Reverse Evolution

• This image shows how horses’ hooves became more primitive over time

Reverse Evolution

The Devolution of Cetaceans• Cetaceans: whales, dolphins, and porpoises • Evolved from an order called Mesonychids, extinct terrestrial

(land dwelling), hoofed, wolf-like carnivores. • Most devolution and evolution theories agree terrestrial

organisms are more advanced than aquatic organisms, and aerial organisms ( with the ability to fly) are the most advanced of the common organisms.

Reverse Evolution

The Devolution of Cetaceans• So modern whales have in devolved from their ancient

ancestors due to environmental pressures and the benefits gained from increased swimming abilities and living in a marine environment. – Caused by a series of advantageous mutations which slowly changed

their spinal column into a vertically moving tail

Reverse Evolution

This is the transformation that transformed ancient Mesonychids into the modern whale. This devolution occurs as we move forward in time.

Reverse Evolution

The Case of The Three Spine Stickleback

• Throughout the 19th and 20th centuries, Lake Washington became highly polluted due to industrial advancements and human carelessness

• Three Spine Sticklebacks are small fish that inhabit the lake that are prey to the larger trout

• Due to the murkiness of the water, the stickleback fish lost the need for its heavy armor plating; this is because it was no longer visible to its predators

Reverse Evolution

The Case of The Three Spine Stickleback• However, in the 1960s a massive government clean up of Lake

Washington led the water to return to its crystal clear nature• This proved disastrous for the stickleback, once again in plain sight of

predators, but now unarmored• Within a decade, huge numbers of stickleback began to be born with

armored plating for protection

Reverse Evolution

The Case of the Three Spine Stickleback

• This means, in order to survive, the sticklebacks readapted to the clear water, re-growing the lost armor

• Today, 49% of sticklebacks in Lake Washington are fully armored, 35% partially armored

• The phenomenon has proved to scientists not only can organisms evolve due to environmental circumstances, but also devolve

Reverse Evolution

• The clear difference in the amount of plating is due to the fish adapting to it’s environment through evolution and devolution

Reverse Evolution

Artificial Devolution• Like many other scientific theories, devolution can be grouped into both a

natural and artificial groups• Natural Devolution: when an organism in nature reverts to a more

primitive form to adapt to its environment• Artificial Devolution: when scientists alter an organism’s DNA in an early

stage to result in a more primitive form of the organism

Reverse Evolution

Snouted Chickens• Because chickens descended from dinosaurs/reptiles through

genetic changes, scientists were able to altar the DNA of chicken embryos so to take on long lost qualities

• Birds lost their snouts in the late cretaceous period, developing beaks, separating them from relatives like crocodilian

• The alterations performed by these scientists lead the embryos to develop a toothless, crocodile-like snout

Reverse Evolution

• Skeletons of a chicken and a velociraptor have many similarities; it is probably a distant relative

Reverse Evolution

Snouted Chickens

• The experiment hasn’t created dinosaurs, however it has shown scientists have the ability to revert evolution

• Paleontologists will continue with similar experiments in hopes go as far as dinosaur/reptile like hands and tails in chickens, Tyrannosaurus's closest living relative

Reverse Evolution

Restoring Genes In Mice• For thousands of years, mice have lacked the ability to convey facial

expressions due to the loss of the an ancient gene known as Hoxb1• Thus when a puff of air is blown in a mouse’s face, it is unable to

react• In 2006, scientists at the University of Utah, were successfully able

to insert this gene back into the mice, through a current gene called Hoxa1

• After the experiment was complete, mice were able to blink, twitch their whiskers, and fold their ears once again

Reverse Evolution