Final answer:
In the 1960s, habitat destruction and introduction of non-native predatory fish significantly affected the pupfish. Habitat alterations, such as deforestation and water diversions, changed pupfish ecosystems. Additionally, pollution and cloudy water from human activities could disrupt mating patterns.
Step-by-step explanation:
In the 1960s, two human activities that affected the pupfish were habitat destruction and the introduction of predatory fish. Due to human impact on aquatic systems, habitat destruction was a significant factor, as activities such as deforestation and water diversion caused changes to the ecosystems pupfish lived in. Additionally, the introduction of non-native species, often through aquaculture or aquarium release, could lead to increased predation pressures on native fish populations such as the pupfish. Pollution also played a role in affecting the visibility of water, which could interfere with mating rituals and species identification, as noted in a hypothetical example regarding lake cloudiness impeding the ability of fish to choose partners from their own species after undergoing sympatric speciation.