Those whom the gods would destroy, they first make mad.
As with so much else I write here, what follows should be taken as intuitive speculative (empirical) theory.
Like forest fires, extinction is built into the gaiasphere: limited or even widespread species destruction to stabilise the whole. Living species intertwine closely with each other. Their nutrition, behaviour, even waste management depend upon a detailed interconnectivity. The effects of very small changes quickly magnify: not unlike DDT absorption up the food chain but these effects ripple through every part of the interconnectivity, not only those related by food consumption. As well, when applied to an already stressed system (say, by meteor strike), these effects magnify logarithmically not once, but twice (the second time when the stressing effects are removed): resulting in sudden and widespread species die-off of up to 90% of all extant species when the originally stressing effects are removed.
Humankind itself is the stressing factor in this age of the earth. Among a small but significant fraction of the population whole, the local social ideation has been shifting behaviour for some generations now to an anti-evolutionary (and perhaps directly and actively self-destructive) mode. Further, the nature of this ideation is such as to self-propagate by inserting itself within the living structure of other types of societies and using the existing frameworks to transform the goals of their growing and reproductive elements. (Yes, this is a viral model.)
Several parts to this. Running short of time, start with this one:
Complex species, and especially those whose major evolutionary adaptations include their ability to think, rely on teaching/learning for their survival, implemented primarily within such basic social structures as the family. Their continued existence requires information-fixing (in the sense of nitrogen fixing) within families and/or other primary social structures, in parallel with information-reassessment by each new generation. The longer the period of child development and dependency, the higher the evolutionary value placed not (solely) upon reproductive capacity, but on life wisdom of the older generations and their ability to transmit it.
Since there remains no instinct to successfully raise offspring (it has been superceded by teaching), an established societal structure is essential to ensuring such transmission, and thus the continued viability of future generations. However, societal growth of individual economic wealth correlates negatively with every family structure except the nuclear family and the single parent ... and positively with increasing social isolation of the elderly.