Why would that be a better hypothesis? It seems likely that for all of these factors the arrow of causality would go in both directions. Being wealthier allows

Why would that be a better hypothesis? It seems likely that for all of these factors the arrow of causality would go in both directions. Being wealthier allows you to spend more time, money and effort on health (though with diminishing returns). You can spend more time and effort learning Being healthier, allows you do physically work more both short and long term. There are also cognitive benefits from healthy activities like exercise. Being born with a high IQ and raised well, lets you potentially make better health choices and being smarter allows greater access to financially beneficial activities. They are interlinked.