Narrative
Description of The Sphere of Life Poster
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The history of life on Earth is a record reconstructed from distant fossil relatives and comparisons among living cousins using various physical, developmental, and molecular data. From first appearance some 3,600 million years ago, life has changed considerably and diversified widely into the variety of different species alive today. This so-called "evolutionary tree of life" more accurately resembles parts of a broad, spherical bush composed of branching lines spreading out from the center. All organisms alive today are located at the growing edge of the sphere and equidistant from its point of origin in the middle where we find the first common ancestor.
The design incorporates each of the three domains of life: Archaea, Bacteria, and Eukarya are represented en masse as expanding lineages from the center of the sphere, the origin of biological life on Earth, to the present at the surface of the sphere. When an individual dies, a branch ends. When mass extinctions occur, many branches end simultaneously (such as was the case for the dinosaurs). Still others survive and split to produce new branches with the passage of time. Humans are, in the biological sense, merely one of millions of species of living organisms now inhabiting the planet. We are part of an extensive pattern of life sharing descent with modification from common ancestors, thus passing on our genes through time.
Beginning with most recent time in the magnified circle at lower left, we view recognizable human genealogy--in the case shown here, the extended lineage of the English Royal family. Moving to the circles at right, we broaden our view through successively larger periods of time to include more recent ancestors from the distant past. From hominids to primates, mammals, and vertebrates, we travel back in time along our ancestral heritage. We relate ourselves to modern-day living cousins such as chimpanzees, kangaroos, lemurs, and frogs. This helps to define our place among other living creatures and demonstrates that we are not direct descendants of chimpanzees or apes but instead share a common ancestor with them.
This poster design incorporates a way of revising the ongoing changes in phylogeny--the evolutionary history of living systems--as new bones are unearthed and new gene mutations traced back. As new data become available, we will post downloadable pdf documents at www.tufts.edu/as/wright_center/svl/poster/posts.html which can then be printed and attached to the original poster, thus keeping it constantly updated with the latest changing developments in this dynamic and fascinating subject.
Poster design and execution by Wright Fellow John Banister-Marx and artist Nick Deamer, Wright Center for Science Education, Tufts University .