Alignment Wall

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Perhaps the most novel part of the design is the Alignment Wall.

Inside every cell of every living thing, there is DNA. DNA stores genetic information, the instructions for making an organism. The DNA molecule is itself made up of a series of smaller molecules, called nucleotides. There are four of these- adenine, cytosine, guanine, and thymine. These molecules can be thought of as four letters- A, C, G, and T- which are here represented by four different colours. These letters in turn spell out three-letter ‘words.’ The words are then strung together to make genes. In building evolutionary trees, scientists line these sequences up- they align them- to look for similarities and differences with A, C, G and T color coded for easy inspection. The resulting pattern, called an alignment, looks like abstract art- and we thought that perhaps it could function as abstract art.

The alignment wall contains DNA sequence data for a single gene called 16S. 16S performs a vital function- it codes for a component of a molecular machine called a ribosome, which helps translate the sequences in DNA into the proteins we are composed of. It’s a vital function, so all organisms on earth have some variant of this gene.

Here, we see DNA instructions that help to build eight species. Each row of tiles represents the 16S gene sequence for a different species. From top to bottom, these are:

Human, Homo sapiens (human being),

Neanderthal, Homo neanderthalensis (Neanderthal)

Chimpanzee, Pan troglodytes (chimpanzee)

Domestic Dog, Canis lupus domesticus (domestic dog)

Darwin’s Finch, Geospiza magnirostris (Darwin’s Finch)

Lonesome George the Galapagos Tortoise, Geochelone abingdonii

Wallace’s Flying Frog, Rhacophorus nigrapalmatus

Coelacanth Fish, Latimeria chalumnae

As you can see, each species has a different DNA sequence. The 16S gene is copied and passed on from mother to offspring, but errors- mutations- can creep in when the code is copied.  Some of these errors are harmless, others are helpful and tend to be retained. Over time, the gene sequences accumulate more and more differences- they evolve. You can see that the human and Neanderthal genes are almost identical- little evolution separates us. Of the living species, chimpanzee is most similar to human, dogs are more distinct. Many mutations, accumulated over hundreds of millions of years of evolution, separate a human from a fish. But we can see that fundamental similarities link all the different versions: they are all variants of a single gene sequence, an ancestral gene sequence, that was inherited from an ancestor that lived over 400 million years ago. By tracking the evolution of this gene- and many others- it becomes possible to reconstruct patterns of relationship between living species- a family tree that links humans with extinct hominids, apes, birds, fish, and all other life on earth.

 

The species.

The eight species represented on the wall were chosen because they represent different branches of our family tree, and different aspects of evolution. Some of them are related to us, some of them were part of the story of the discovery of evolution, some of them were bred by us, some of them were wiped out

by us.

 

Homo sapiens. This is you, and us.

 

Homo neanderthalensis. Neanderthals, our closest relatives, died out around 30,000 years ago when modern humans invaded Europe and Asia. They live on, in a fashion: sequencing DNA from the bones of Neanderthals, it was found that Europeans and Asians are about 1-4% Neanderthal, the result of ancient hybridization between Homo sapiens and Homo neanderthalensis. Neanderthals suggest that hybridization may play an important role in evolution.

 

Pan troglodytes. The chimpanzee is our closest living relative. Although our DNA differs from chimpanzees by only a few percent, these mutations code for features such as the ability to learn language and make complex tools which are not seen in chimpanzees.

 

Canis lupus domesticus. Man’s best friend, the domestic dog. Dogs show that all evolution is the result of natural selection; dogs descend from wild wolves, but have been modified by thousands of years of selective breeding by humans to produce the remarkable range of breeds seen today.

 

Geospiza magnirostris. Darwin’s Large Ground Finch is one of the species collected by Darwin during his visit to the Galapagos Islands as naturalist aboard the Beagle, a voyage that would spur his thinking on evolution and lead to the Origin of Species.

 

Geochelone abingdonii. Extinction is part of the story of evolution: the evolution of new species can drive old species extinct, and the extinction of old species can drive the evolution of new ones. Lonesome George the Galapagos tortoise was the last of his species, and died in 2012In the case of Lonesome George, it was the evolution of human beings that ultimately led to the extinction of the species, as habitat destruction and introduced pests in the Galapagos led to the decline of the species.

 

Rhacophorus nigropalmatus. Alfred Russell Wallace, a contemporary and colleague of Darwin’s independently hit upon the idea of natural selection while suffering through a malarial fit in Southeast Asia. Wallace’s Flying Frog, a frog that glides on huge webbed feet, was first collected by Wallace, and named in his honor.

 

Latimeria chalumnae. The coelacanth represents a ‘living fossil’- a group of animals described first from fossils, and then discovered alive deep in ocean. Coelacanths were here long before the dinosaurs, and long after. Hiding in deep, dark waters, its ancestors were barely affected by the asteroid that wiped out 90% of species on Earth. Despite the passage of vast periods of time. Natural selection does not always cause species to change, if a design is effective: if it ain’t broke don’t fix it.