Life is life - whether in a cat, or dog or man. There is no difference between a cat or a man. The idea of difference is a human conception for man's own advantage.
~Sri Aurobindo
The first chapter of Genesis gives human dominion over the animals:
"Rule over the fish of the sea and the birds of the air and over every living creature that moves on the ground". This statement from the Bible has been a long time used argument to justify human's supremacy over animals.

Classical Greece
The first documented pro-animal activist goes back to 6th century BC with Pythagoras, a Greek philosopher. Pythagoras believed in the transmigration of souls between human and animals, a reason for him to treat animals with respect. Ahead of his time, he opposed meat and religious sacrifices from fear of killing the soul of a loved one, or an ancestor.
"Human beings, stop desecrating your bodies with impious foodstuffs. There are crops; there are apples weighing down the branches; and ripening grapes on the vines; there are flavoursome herbs; and those that can be rendered mild and gentle over the flames; and you do not lack flowing milk; or honey fragrant from the flowering thyme. The earth, prodigal of its wealth, supplies you with gentle sustenance, and offers you food without killing or shedding blood." Ovid, "Pythagoras's Teachings: Vegetarianism"
Empedocles, 450 BCE, was another pro-animal activist, who talked against animal slavery and the consumption of meat.
"Slaughter and meat-eating are the most terrible of sins, indeed for him animal slaughter is murder and meat-eating is cannibalism" Empedocles, "Fragments: On Purifications".
In the 4th century BC, one of Aristotle's students, Theophrastus (370 285 BC), disagreed with his teacher arguing that eating animals was wrong because it robbed animals of their life, that animals could reason, sense and feels like humans do. Eating them was therefore unfair.

India
The most ancient law about animal right comes from India. It was proclaimed by King Asoka (274-232 BCE), Emperor of India. He became a Buddhist. "Here (in my domain) no living beings are to be slaughtered or offered in sacrifice" (The Fourteen Rock Edicts.)
India has a long history of non-violence against humans and animals. Jainism is the strictest religion of the world when it comes to committing violence. Animals' right is very high in the scale of what is important. Jains cover their faces to avoid swallowing bugs inadvertently,
and say a prayer every night to ask for forgiveness to animals they might have killed during the day.

Classical Roman Empire
Cicero [106-43BCE], Virgil [70-19BCE] and Plutarch [46-120] were all opposed to human's domination over animals and the cruel used they made of them. In their writings, they plead for humankind to recognize the pain animals were enduring because of humans.

"And for a little peace of flesh we take away their life, we bereave them of their sun and of light, cutting short that race of life which nature had limited and prefixed for them; and more than so, those lamentable and trembling voices which they utter for fear, we suppose to be inarticulate or insignificant sounds, and nothing less than pitiful prayers, supplications, pleas & justifications of those poor innocent creatures, who in their language, every one of them cry." (Plutarch, Morals)

Christianity
St. Chrysostom [c347-407] was against the treatment reserved to animals in the remnants of the Roman Empire. This early father of Christianity opposed this treatment of animals in the arenas in many of his letters.
"Why need I speak of the sort of charm which is found in the horse races? Or in the contests of the wild beasts? For those places too being full of all senseless excitement train the populace to acquire a merciless and savage and inhuman kind of temper, and practise them in seeing men torn in pieces, and blood flowing, and the ferocity of wild beasts confounding all things. Now all these our wise lawgivers from the beginning introduced, being so many plagues! And our cities applaud and admirebut which clearly and confessedly are abominable." (St. Chrysostom, Homily XII. 1 Cor. iv. 6)

In the Middle Ages and until Renaissance, animals rights are left in the dark, nobody raises a voice to protest the treatment made to animals.

Enlightening Era
One of the first defender of animal right during Enlightening Era is Jean-Jacques Rousseau (1712- 1778). Descartes had stated that animals have neither souls nor minds, and therefore cannot think or even feel pain. Rousseau argues that animals are sensitive beings, they seek to participate in the natural rights of the universe and as such, man is subject to some sort of duties toward them," specifically "one [has] the right not to be needlessly mistreated by the other." Rousseau. "Discourse on Inequality" 1754
Scottish writer John Oswald (1760-1793) was another advocate of animal rights. In his "Cry of Nature or an Appeal to Mercy and Justice on Behalf of the Persecuted Animals", he says that the division of work in society was the reason why vegetarism was not more common. He thought that if every person witnessed the death of the animals they ate, vegetarism would become more popular.
Ireland was the first state in modern times to pass a Law for animal right. In 1635, the "Act against Plowing by the Tayle, and Pulling the Wooll off Living Sheep", was made public by Thomas Wentworth.
The first animal protection right law of the US was passed in 1641 in Massachusetts. Nathaniel Ward's, "Off the Bruite Creature," Liberty 92 and 93 of the Body of Liberties, states that:
"92 No man shall exercise any Tirranny or Crueltie towards any bruite Creature which are usuallie kept for man's use.
93 If any man shall have occasion to leade or drive Cattel from place to place that is far of, so that they be weary, or hungry, or fall sick, or lambe, it shall be lawful to rest or refresh them, for a competent time, in any open place that I not Corne, meadow, or inclosed for some peculiar use."
Many pleas for legislation in the US were heard from that time on: 1737, 1749, 1789, 1796, 1798, 1799 have all seen many request made by influent man at the time that inhumane treatment of animals should be legislated in the US, without success. Some bills were passes as soon as 1800, preventing bating bulls, and "malicious cruelty to animals". Richard Martin's 1822 Bill to Prevent the Cruel and Improper Treatment of Cattle was the first real success in animal right legislation in 1822.
At the same time in Europe, Schopenhauer argues that animals have the same spirit as humans, though lacking reason. He thus pleads for consideration to be given to animals in morality, and he opposed vivisection as a means to experiment medical research.
Britain founded the first Society for the Prevention of Cruelty to Animals in 1824. The same group sprang to several European countries and finally reached New York in 1866. Henry Salt wrote in 1898 the first contemporary book on animal right, "Animals' Rights: Considered in Relation to Social Progress."

Modern Times
In 1933, one of the first laws enacted by national socialist (Nazi) party was one of animal protection.
But the modern animal liberation movement was really born in the 70's, when Oxford university philosophers began to question if moral rights of animals were necessarily inferior to that of human beings. The term speciesism was them coined to describe those who believe that the human species had superior rights to animals. Peter Singer then formulates the basic arguments on animal liberation in his 1975 book "Animal Liberation", the "bible" of the animal rights liberation movement.
In the 80's and 90's, the movement widens to many different professional and academic groups, and all over the world. In the 80's and 90's, the movement widened to many different professional and academic groups, and all over the world.

References
"Animal right history" http://www.animalrightshistory .org/arh/index_notes.htm
The Bible Gateway's, "Genesis, chapter 1", http://www.biblegateway.com/pa ssage/?search=Genesis
"Janisme, Jan, Mahvira, Svastika, Prires... " www.jainisme.com
"Jainism: Principles, Tradition and Practices" www.cs.colostate.edu/~malaiya/ jainhlinks.html
"Peta.org", http://www.peta.org/
Wikipedia, "Animal rights", http://en.wikipedia.org/wiki/A nimal_rights