The question Losos asks, and tries to answer, is this: can we predict evolution? Are certain things inevitable in development — birds, humans, antibiotic resistance, etc, etc? He writes engagingly about field work, experiments, thought experiments, the various theories and people who have supported them… I definitely want to do more reading on this.
Am I convinced? Well, I’m not sure Losos is convinced that evolution can be predicted in detail; he presents some good evidence that suggests that you can predict the sorts of changes in gene function that will be beneficial in a certain environment, but that you can’t predict exactly how those changes will come about. Sometimes one gene might be altered, sometimes another. The phenotype is predictable (unsurprisingly: look for what would benefit the species in breeding successfully) but the genotype is not, unless it’s a fairly simple case of one particular molecular switch needing to be flipped on or off. There is a great deal of contingency in the process of evolution: Gould was (at least to some extent) correct in suggesting that we can’t “rewind the tape of life” and then see things proceed in exactly the same way.
As with determinism in any sense, I generally believe that if all factors were known, we would also know the result. I’m just not sure we can know those factors (and I dislike and squirm away from applying it to human ethics — our actions may be caused by previous events, but we don’t experience the process that way, so it’s irrelevant in how to be moral) — especially given events on a quantum level.