Science denial ‘memes’ are a viral form of communication that attempt to undermine complex scientific ideas using memorable soundbites. These memes misrepresent the scientific content they are ‘debunking’, making responding to them challenging. To identify common strategies, we analysed Twitter/X responses to the anti-evolution meme ‘why are there still monkeys?’. Strategies included literal explanations about why the reasoning behind the meme is flawed, and analogies that mirror the original meme to varying degrees (e.g. in structure and/or domain). We evaluated different response strategies using an experiment with participants from the United States who either endorsed or denied evolution. Participants rated their understanding of the original meme and different response strategies, and how effective and persuasive they found them. Across participants, literal explanations were rated more understandable, effective and persuasive than analogical responses. Memed rebuttals may thus be a counter-productive strategy for responding to science denial online.