It is not widely known, but chickens have been growing this way since the 1800's. In fact, back then chickens were the size of a microbe, and the word "chicken" used to refer to the disease that they spread, one notable symptom of which being tremors (hence the association of the word "chicken" with fear). In the late 19nth century and early 20th chickens reached the size of insects, and have since continued to grow as per OP's image.
Unfortunately, not many are aware of the existential risk chickens pose, since if they continued to grow at this rate, they would eventually reach godzilla proportions and likely assault cities. Recent studies indicate that as early as the 2050's chickens might become large enough to be able to smash a tank with their beak; and in general the "chicken growth" problem has been on a meteoric rise as an academic field, recently surpassing cancer cure research by number of studies published per year. Popular currents in this field include shrinking potions, fox enlargements and giant fry pans for massive egg handling. The origins of this rapid chicken evolution however remains unknown, and this mystery has given birth to plentiful speculation and even religions, for example Galluism, which states that chickens are in fact immortal, eternal beings that reincarnate (hence solving the chicken-egg problem) and that they are the original Elohim referred to in ancient babilonian scripture and the bible.
Another largely forgotten fact is that cows, on the other hand, are shrinking; albeit at a slower pace. Millennia ago they used to be the size of mountains, which is likely the reason behind their sacrality in hinduism.