The statement "Indus Valley was the first settlement of the big civilization" requires critical examination. While the Indus Valley Civilization (IVC) was undoubtedly one of the earliest and most extensive ancient civilizations, asserting it as the absolute first settlement of a 'big civilization' globally is inaccurate. However, it was a pioneering civilization in its own right, demonstrating remarkable achievements.

Strengths of the IVC as a 'Big Civilization':

1. Urban Planning and Infrastructure: The IVC, particularly its major cities like Mohenjo-Daro and Harappa, exhibited extraordinary urban planning. Cities were laid out on a grid pattern, featured sophisticated drainage and water management systems, public baths (like the Great Bath), and granaries. This level of civic organization was highly advanced for its time.
2. Scale and Extent: The IVC was one of the three early civilizations of the Ancient Near East and South Asia, alongside Ancient Egypt and Mesopotamia. It was the most widespread of the three, covering an area larger than the other two combined, stretching across modern-day Pakistan, Afghanistan, and northwest India.
3. Technological Advancement: The civilization demonstrated significant technological prowess, evident in standardized brick sizes (a 1:2:4 ratio), advanced metallurgy (copper, bronze, gold, silver), intricate seals with undeciphered script, and precise weights and measures.
4. Social Complexity: The presence of distinct residential areas, public structures, craft specialization (pottery, bead-making, metallurgy), and a probable administrative hierarchy suggests a complex social organization and division of labor.
5. Trade Networks: The IVC engaged in extensive trade relations with contemporary civilizations like Mesopotamia, Oman, and Central Asia, indicated by the discovery of Indus seals and artifacts in these regions and foreign artifacts within IVC sites.

Critical Commentary on "First Settlement":

1. Contemporaneity with Other Civilizations: The mature phase of the IVC (c. 2500-1900 BCE) was broadly contemporary with other major 'big civilizations.' The Sumerian civilization in Mesopotamia, for instance, emerged earlier, with its first city-states like Uruk developing around 3500-3000 BCE. Mesopotamia saw the development of writing (cuneiform), monumental architecture (ziggurats), and complex administrative systems before the mature phase of the IVC. Similarly, the Old Kingdom of Egypt (c. 2686-2181 BCE) also predates or is contemporary with the IVC's peak.
2. Pre-Harappan Phases within the Indus Region: Within the Indus region itself, there were earlier, smaller settlements and cultures (e.g., Mehrgarh, Amri, Kot Diji) that predated the mature Harappan phase. These cultures, often termed 'Early Harappan' or 'Pre-Harappan,' laid the groundwork for the later urban development, demonstrating a gradual evolution rather than a sudden 'first settlement' of a big civilization. Mehrgarh, for example, shows evidence of early agriculture and settled life as early as 7000 BCE.
3. Definition of "First": If "first settlement" implies the absolute earliest human settlement, then that would be much older, dating back to the Paleolithic or Mesolithic periods, long before any 'big civilization.' If it means the first urban settlement, then Mesopotamia generally holds that distinction.
4. Independent Emergence: While there were interactions and trade, the IVC developed largely independently, with its own unique characteristics, distinct from Mesopotamia and Egypt. It is considered a primary civilization, meaning it developed indigenously rather than being derived from another.

In conclusion, while the Indus Valley Civilization was undeniably one of the earliest, largest, and most sophisticated 'big civilizations' with remarkable achievements in urban planning and technology, it was not the first settlement of a big civilization globally. Mesopotamia generally holds that distinction in terms of the earliest urban development and complex societal structures. The IVC represents an independent and highly advanced development in the history of human civilization, but within a broader global context of multiple, contemporaneous early civilizations.