What if the orbit of Darwinism should be a little too circular? What if species should offer residual phænomena, here and there, not explicable by natural selection? Twenty years hence naturalists may be in a position to say whether this is, or is not, the case; but in either event they will owe the author of "The Origin of Species" an immense debt of gratitude...... And viewed as a whole, we do not believe that, since the publication of Von Baer's "Researches on Development," thirty years ago, any work has appeared calculated to exert so large an influence, not only on the future of Biology, but in extending the domination of Science over regions of thought into which she has, as yet, hardly penetrated.
同時代的另一個演化理論家是克魯泡特金，在他的互助論：演化的一種因素（Mutual Aid: A Factor of Evolution）一書裡，他支持和赫胥黎主張相反的達爾文主義。他的理論以他所見人類與動物以合作為生存機制的普遍為中心。他以生物和社會性的論點來顯出助長演化的主因是在自由聯合的社會和團體裡自由合作的個體。這是為了反駁演化的核心是激烈競爭的論點，競爭理論為當時流行的政治、經濟和社會理論提供了合理性；而盛行的對於達爾文主義的詮釋，例如克魯泡特金視為對手的赫胥黎的詮釋，克魯泡特金的達爾文主義概念可以以以下的引言總結：
In the animal world we have seen that the vast majority of species live in societies, and that they find in association the best arms for the struggle for life: understood, of course, in its wide Darwinian sense– not as a struggle for the sheer means of existence, but as a struggle against all natural conditions unfavourable to the species. The animal species, in which individual struggle has been reduced to its narrowest limits, and the practice of mutual aid has attained the greatest development, are invariably the most numerous, the most prosperous, and the most open to further progress. The mutual protection which is obtained in this case, the possibility of attaining old age and of accumulating experience, the higher intellectual development, and the further growth of sociable habits, secure the maintenance of the species, its extension, and its further progressive evolution. The unsociable species, on the contrary, are doomed to decay.
—— Peter Kropotkin Mutual Aid: A Factor of Evolution (1902), Conclusion.