其实可以将这句话缩短为Advance could be made by the emergency of creatures,而 in the scale of evolution along such lines as these只不过修饰的是Advance这个主语,
only强调的是这种发展前进的唯一性,with more and more complicated instincts.修饰的是creatures,这样很简单就看出这句话的意思：以如此路线规模的变革所带来的进步只有拥有更复杂天性的生物 才能做到.
in the scale of就是 “ 以.的规模”.