Abstract - Our living world is the result of a complex history spanning billions of years. Scientists have access to artifacts of this history, namely the fossil record and the genomes of many different living organisms. But there are surprisingly limited means with which to infer critical evolutionary elements in the deep past that resulted in modern biota. It is particularly difficult to reconcile (sometimes cryptic) fossil morphology on one hand, and genetic composition and diversification over time on the other, when so little about the behavior of ancestral organisms can be reconstructed that would link these disparate datasets. Did past forms of life function, behave or evolve similarly to life today? Did the biology of past organisms inherently limit their ability to evolve into modern forms? In this chalk talk I will introduce a novel experimental system whereby genomes in extant organisms are engineered with inferred ancient gene sequences. The resulting ancient-modern hybrid organisms are monitored to assess the phenotype changes, if any, that the ancient sequences impose on the organism. The reconstructed genotypes and phenotypes are then compared and interpreted against biosignatures recorded in ancient rocks. Our objective is to explore how this particular use of synthetic biology can shed more light onto critical problems in life's early history for which the fossil and gene records fall short of full explanation.