It seems humans reached Madagascar not 2400 to 4000 years ago but as early as 6000years ago, acoording to recent studied, reported by Rhett Butler , a journalist, not the actor!
Follow the link please to read the article
https://news.mongabay.com/2018/09/humans-reached-madagascar-6000-years-earlier-than-previously-thought/
on Mongabay web site
