Just finished reading the book above. I only link to it in order to advocate that you do not purchase it or read it.
I must have read well over 40+ books by now on the extinction cycle, many of them focused on the recently discovered extinction event at the start of our interglacial. The more I read on the subject the less respect I have for everybody else and the more respect I have for Robert Felix.
Nearly every single one of the books I have read posits a collision/comet/meteor theory, a safe hypothesis to be sure since it is the same inadequate explanation I have heard offered by everybody else. The book above actually has the naivete to postulate that this cosmic collision was neatly distributed at 12,000 year intervals in order to match up with the observed chronology.
The thing in each and every one of these books that always causes me to wince and cringe with disgust is when they all end with practically the same sentence : "Oh yeah, and in addition to all this it appears there was a magnetic reversal or excursion around the same time this all happened. What a coincidence, whooda thunkit."
I advocate you read none of the other books I have read, they are shamefully deficient rubbish. Robert Felix's book is the refutation of that rubbish and the only book I would recommend to you.