Dark spots are caused by overexposure to the sun. It can be down to hormonal changes and it can otherwise be an oxidation process from whatever we're using on our skin.
If you veer more towards using natural skin care, protect the skin with a natural alternative to the chemicals that we've got in sunscreens like raspberry seed oil.
Dark marks can be down to the aging process. But it's also down to what we're eating and what we're applying to our skin. If you haven't seen my video on YouTube, 'What the Health Next', watch that video and get lots of information on what some conventional products are actually doing to our skin and to our bodies.