This may irk a lot. But I am being dead objective. By this I do not mean they are superior but that the fact that their intelligence is the most balanced. This has been seen in history where they were able to easily adapt themselves according to the situation and place and still retain their essence. I can speculate that their intelligence is the maximum achievable in humans. There are of course many types of intelligence but with regard to all round and balanced intelligence the brahmins clearly stand apart. I would even go to the extent and say that they are from a different evolved star system and were attracted to the great spiritual earth.
Comments and criticisms welcome
Human race has been the result of evolutionary adaptation. The current switch to homosapiens race is a gradual evolution that happened when species gets divided physically and grow into a different species due to different evolutionary adaptation needs. Ability to process information, use external environment to build tools, which in turn puts pressure on more logical processing needs is also a gradual evolutionary growth. That's why they say vasudha-iva-kutumbakam. All beings in earth are one family. We can also say prajnAnam brahma. All life are creation/expansion of that consciousness.
What differentiates human beings is their ability to witness their own thoughts, ability to analyze information from other's perspectives, ability to have a sAksi in their manas/mind. This ability is what creates and evolves new things and is with all humans. aham-brahma-asmi. This is for all human beings.
In the varNa system brAhmana are knowledge providers. Anyone who creates new knowledge is a brAhman. But brahmin jAti, which is a hereditary system, is not same as brAhmana varNa. brahmin jAti was formed only to preserve vedic texts. Their only job was to recite vedic texts accurately and transmit it to future generations as a human tape-recorder. Since people believed Vedic texts have huge knowledge that could not be understood fully, but need to preserved, they formed this brahmin jAti to do only that. They were protected and nourished by royal decrees, grants of lands etc.
brahmin jAti whose only job was preservation of vedas always had to rely on others for living. So they had to be skilled in adaptation and have to continuously migrate to new lands seeking sustenance. That's how tambrahms came into being. Migration and adaptation have been the hall-marks of tambrahms as a jAti, as they never were really owners of anything.
If you are referring to brahmin jAti, then that jAti does not exist now in most parts, as they are no longer into vedic preservation. What they are using is their skills in adaptation and migration. They adapted to rulers of different religions, nationalities and cultures and survived in the past. When British came, they were the first ones to serve the British. When INC started, they were the first one's to participate. They were the first ones to migrate to US and Europe seeking greener pastures. But in this process, they have to leave their core task of preserving vedas, for most parts.
If you are referring to brAhmana varNa, then by definition any one who provides knowledge is brAhman.
Nobody by birth can claim to superior intelligence in this planet. Most of our past literatures in samskrt or tamil are not from brahmin jAtis. Our scientific inventions and discoveries of the past were also not always from brahmin jAti, as their job was to recite vedic scriptures only. As early adapters of western science, culture, politics and technologies, we find them in many top echelons of society today. That's just an early mover advantage.
Just my humble view.