Edward Blyth wrote this in 1835. He published several articles which were read by C. Darwin. After that, Darwin published his book in 1859. He just took the ideas from Blyth , Lamarck, Tremaux, Malthus and Wallace.He used the knowledge and ideas that were previously developed. With this, the social and economics ideas of the Victorian  society were projected in nature.

Now ,  the Text from Blyth:

It is a general law of nature for all creatures to propagate the like of
themselves: and this extends even to the most trivial minutiae, to the
slightest individual peculiarities; and thus, among ourselves, we see a
family likeness transmitted from generation to generation. When two
animals are matched together, each remarkable for a certain given
peculiarity, no matter how trivial, there is also a decided tendency in
nature for that peculiarity to increase; and if the produce of these
animals be set apart, and only those in which the same peculiarity is
most apparent, be selected to breed from, the next generation will
possess it in a still more remarkable degree: and so on, till at length
the variety I designate a breed, is formed, which may be very unlike
the original type.
The examples of this class of varieties must be too obvious to need
specification: many of the varieties of cattle, and, in all probability,
the greater number of those of domestic pigeons, have been
generally brought about in this manner. It is worthy of remark,however, that the original and typical form of an animal is in great
measure kept up by the same identical means by which a true breed
is produced. The original form of a species is unquestionably better
adapted to its natural habits than any modification of that form;
and, as the sexual passions excite to rivalry and conflict, and the
stronger must always prevail over the weaker, the latter in a state of
nature, is allowed but few opportunities of continuing its race. In a
large herd of cattle, the strongest bull drives from him all the
younger and weaker individuals of his own sex, and remains sole
master of the herd; so that all the young which are produced must
have had their origin from one which possessed the maximum of
power and physical strength; and which, consequently, in the
struggle for existence, was the best able to maintain his ground, and
defend himself from every enemy. In like manner, among animals
which procure their food by means of their agility, strength, or
delicacy of sense, the one best organised must always obtain the
greatest quantity, and must, therefore, become physically the
strongest, and be thus enabled by routing its opponents, to transmit
its superior qualities to a greater number of offspring.


Blyth. “Attempt to Classify”, pp. 45-46.

en “Charles Darwin’s Debt to Malthus and Edward Blyth” JOEL S. SCHWARTZ. Journal of the History of Biology, vol. 7, no. 2 (Fall 1974), pp. 301-318