We would not have developed near as fast without the steam engine, the internal combustion engine would still have been invented and put into service but we would have spent many more years with the horse and buggy. read more
If a 'steam engine' must have moving parts and do useful work, then Thomas Newcomen, who built a more advanced 'fire engine' that operated with steam power to raise water from mines, would be considered the one who invented the steam engine. read more