In the first place, without the productivity gains that fossil fuels have enabled, the planet’s human population would never have been able to get as high as it has as quickly as it has. For one example, the mega-cities that now dot the globe must all be supplied with food that isn’t grown (for the most part) within the city limits. It’s doubtful that human and animal-powered transport could capably and reliably service so many inhabitants as regularly as trucks and trains now do. So those cities wouldn’t be there (there wouldn’t be any need for them in the first place without large-scale fossil-fuel-powered industry), and the people wouldn’t exist if they couldn’t feed themselves. (And even with the huge numbers of people that would be required to plant and harvest crops, there isn’t enough farmland in the world to support so much humanity “working the fields”.)
But I think that whales would have been hunted to extinction, because as good as capitalism is at many things, it has not resolved “the problem of the commons”.