Astronomer: Proponents of the hypothesis that life evolved extraterrestrially and drifted here in spores point out that, 3. 8 billion years ago, Earth was bombarded by meteorites that would have destroyed any life already here. Yet 3. 5 billion years ago, Earth had life forms complex enough to leave fossil remains. Such life could not have evolved here in the 0. 3 billion years following the meteorite bombardments, they claim. There is good reason to regard their hypothesis as false, however, for they merely offer empirical arguments against the view that life evolved on Earth; neither they nor anyone else has provided positive support for the extraterrestrial-spore theory of the origin of terrestrial life. The reasoning in the astronomer's argument is flawed because the argument ['attempts to derive a conclusion from premises that contradict it', 'concludes, simply because there is no evidence in favor of a hypothesis, that there is evidence against that hypothesis', "grants the truth of claims that are made by the advocates of the hypothesis but that do nothing to strengthen the astronomer's own argument", 'reasons that a hypothesis is false simply because there is another hypothesis that is equally likely to be true']