The evolutionary theory of law has an intriguing similarity between the processes of biological evolution and the emergence of legal systems. Much like organisms adapt to changing environments for survival and prosperity, legal systems also adapt in response to social changes and shifting needs.

It takes the view that legal rules, institutions, and practices are not static entities, but dynamic phenomena that constantly evolve through interaction with their surroundings. Like genetic variation among biological populations, legal systems display variation in their rules, customs, and structures as they reflect the unique cultural, historical, and social environments within which they function.

Such selection pressures, resembling natural selection, operate upon these legal elements, which determine the elements that uphold the social order, stability, and legitimacy while purging the ones that serve none of the purposes or are obsolete.

Evolutionary mechanisms such as legislation, judicial precedent and cultural transmission are responsible for the cross-generational transmission of successful legal innovations for the purpose of continued existence as well as gradual change.

Hence, the evolutional theory of law provides an effective framework for analyzing the organic growth of legal systems and the resulting tensions between tradition and change in the pursuit of justice and social harmony.

Explanation:
The evolutionary theory of law is effectively demonstrated through the development of contract law. Starting out as a simple, informal practice in ancient societies, it has evolved into a complex system that effectively manages the ever-growing complexity of transactions. From the Babylonians and Romans in early civilizations to present times, contract law has continuously adapted to changing societal norms and has successfully accommodated new agreements and challenges, such as those presented by the Industrial Revolution and globalization.

This process of variation, selection, inheritance, and adaptation has refined contract law and showcases its dynamic nature and ability to respond to the changing needs of society, thus exemplifying the core principles of the evolutionary theory of law.

Oliver Wendell Holmes Jr.:
Oliver Wendell Holmes Jr., a highly influential American jurist who served as an Associate Justice of the Supreme Court of the United States from 1902 to 1932, is often credited as the 'father' of the evolutionary theory of law. Although he did not explicitly formulate a comprehensive theory of law based on evolution, Holmes' writings and legal decisions emphasized the evolutionary nature of law. In his renowned work

'The Common Law' (1881), Holmes put forth the concept that law is not static but rather evolves over time in response to societal, economic, and cultural changes. He famously described the common law as a process of 'judicial brooding' over the unorganized material of the law and underscored the importance of considering the historical development and social context of legal principles.

This emphasis on the evolutionary character of law laid the foundation for later scholars to develop more formalized theories of evolutionary jurisprudence, drawing from diverse fields such as biology, psychology, and anthropology. While Holmes may not have been the sole originator of evolutionary legal theory, his contributions played a pivotal role in shaping its fundamental principles.

Key Principles:
Key principles of the evolutionary theory of law include:

• Variation: The legal systems differ among one another with regard to their laws, institutional frameworks, and procedures due to different cultures, history, and social settings.
   
• Selection: Legal norms and institutions are subject to pressure of selection, that is, the law is formed, develops and changes based on its effectiveness in the social order of society, resolution of disputes, and the needs of society.
   
• One example is a legal system that offers procedures for conflict resolution which are both effective and impartial will be left and be more developed while a system that lacks a mechanism for conflict resolution may have to be discarded as an option. In a similar way, legal norms that comply with existing cultural values and are corresponding with social norms will have greater support from the society to be implemented and enforced.
   
• Inheritance: Legal systems hand down the current rules, norms, and institution structures to the next generation through legislative process, judicial precedents, and cultural transmission.
   
• Adaptation: The legal systems develop over time when they are adapting to the new changes in society, technology, as well to the other external issues. Weak legal norms and institutions are naturally shed away, while strong ones are continued and developed over time.
   
• Continuity and Change: Legal evolution rests on the duality of continuity and change where persistent original principles and institutions are occasionally replaced or altered by new challenges and fresh opportunities.

Supporters of the concept that law is a product of evolution believe that taking an evolutionary viewpoint can offer valuable perspectives on the evolution, operation, and effectiveness of legal systems. By comprehending the factors responsible for change, selection, inheritance, and adjustment, it is possible to enhance the ability of experts and decision-makers to predict the impact of new issues, dangers, or obstacles on future legal systems.

Criticism:
Some critics of the evolutionary theory of law argue that although it provides a useful metaphorical framework for understanding the development of law, it oversimplifies the complexities and fails to explore the role of human agency, power relations, and ideological conflicts in the evolution of legal systems. They point out that viewing law as a purely adaptive mechanism, a tool in the hands of the politicians, special interest groups, and the powerful that shape laws to their own purposes is shortsighted.

Besides, the critics also point out to the use of teleological reasoning that is inherent in evolutionary analogies, and they warn us about the common assumption that evolution in legal systems must result in higher efficiencies or justice. Moreover, the theory would probably not take note of the meaning of the discontinuities, ruptures and revolutions in legal development and would rather put the focus on historical contingencies and contingent events, which shape the historical trajectories in the legal development.

Therefore, legal evolution could provide useful guidelines but it is still advised to take a more sophisticated view of legal change which does not only appeal to human nature and power relations but which is more multidimensional and complex.

The persistence of discriminatory laws and practices in various legal systems challenges the expectation of gradual evolution towards inclusivity and equity, undermining the linear progression proposed by the evolutionary theory of law. Despite societal advancements and recognition of human rights principles, discriminatory laws persist due to entrenched power structures, cultural biases, political interests, and resistance to change.

This highlights a limitation of the theory in explaining the failure to eradicate discrimination, prompting critics to advocate for deliberate efforts such as legislative reforms, judicial interventions, and grassroots activism to address systemic injustices and promote social justice.

Conclusion:
The evolutionary theory of law offers valuable insights into the dynamic nature of legal systems, highlighting their ability to adapt to changing societal needs and circumstances over time. By drawing parallels between legal evolution and biological processes, the theory provides a compelling framework for understanding the development of legal norms, institutions, and practices.

However, critics argue that the theory may oversimplify legal evolution by overlooking the role of deliberate human agency, power dynamics, and systemic inequalities in shaping legal systems. Additionally, the theory's reliance on analogies to biological evolution may risk teleological reasoning and underestimate the complexities of legal change. Nonetheless, despite these limitations, the evolutionary theory of law remains a useful tool for analyzing legal development and prompting further inquiry into the interplay between law, society, and culture.